How Many Rolls of Wallpaper Do I Need? Complete Guide

Ordering the wrong amount of wallpaper is expensive. Run short and you’ll pay rush shipping fees, risk getting a different dye lot, or face delays while waiting for backorders. Overbuy and you’ve wasted money on rolls you’ll never use. This guide shows you exactly how many rolls you need.

The Quick Answer

For a 12×10 foot room with 8-foot ceilings using American single rolls:

• Wall perimeter: 44 feet
• Wall area: 352 sq ft
• Usable coverage per roll: ~27 sq ft (after pattern repeat waste)
• Rolls needed: 13 rolls (12.6 rounded up)

For a 10×10 room: 11 rolls.

For a 15×12 room: 17 rolls.

These estimates assume standard 21-inch pattern repeat and one door plus two windows.

The Formula

Wallpaper quantity depends on wall area, usable coverage per roll, and pattern repeat waste:

$\text{Rolls Needed} = \frac{\text{Wall Area}}{\text{Usable Coverage per Roll}}$

$\text{Usable Coverage} = \text{Roll Length} \times \text{Roll Width} - \text{Pattern Repeat Waste}$

Step-by-Step Calculation

1. Measure room perimeter: Add all wall lengths together
2. Calculate wall area: Multiply perimeter by ceiling height
3. Subtract openings: Deduct doors at 21 sq ft and windows at 15 sq ft each
4. Determine usable coverage: American single rolls are 27 inches wide by 27 feet long, which equals 60.75 sq ft gross coverage, but pattern repeat waste reduces this to 25 to 30 sq ft usable
5. Divide and round up: Wall area divided by usable coverage, always round up to the next whole roll

Example: 12×10 Room with 8-Foot Ceilings

1. Perimeter equals 12 plus 10 plus 12 plus 10, which equals 44 feet
2. Wall area equals 44 times 8, which equals 352 sq ft
3. Subtract one door at 21 sq ft and two windows at 15 sq ft each to get 301 sq ft
4. Pattern repeat is 21 inches, so usable coverage per roll is approximately 27 sq ft
5. Rolls needed = 301 ÷ 27 = 11.1 rolls
6. Round up to 12 rolls (always round up, never down)

Add 1 extra roll for errors, corners, or future repairs. Final order: 13 rolls.

Understanding Wallpaper Roll Sizes

Wallpaper comes in different sizes depending on where it’s manufactured. This is important because coverage calculations change based on roll dimensions.

American Single Roll (Standard in US)

Dimensions: 27 inches wide × 27 feet long (approximately 0.69 m × 8.23 m)

Gross coverage: 60.75 sq ft per roll

Usable coverage: 25 to 30 sq ft after waste

Sold as: Usually sold in double-roll bolts, which contain two single rolls’ worth of wallpaper at 27 inches wide by 54 feet long

American Double Roll

Dimensions: 27 inches wide × 54 feet long

Gross coverage: 121.5 sq ft per roll

Usable coverage: 50 to 60 sq ft after waste

Why it matters: Longer strips mean fewer seams and less waste when matching patterns

European Roll (Metric Standard)

Dimensions: 21 inches wide × 33 feet long (approximately 0.53 m × 10.05 m)

Gross coverage: 57.75 sq ft per roll

Usable coverage: 25 to 28 sq ft after waste

Note: European wallpaper is narrower, which means more seams per room compared to American wallpaper

Commercial/Designer Roll

Dimensions: Varies widely, from 20 inches to 36 inches wide, and from 11 yards to 30 yards long

Gross coverage: Check manufacturer specs

Usable coverage: Calculate based on actual dimensions minus pattern repeat

Always check the label for exact dimensions. Don’t assume all wallpaper uses American standard sizing.

Single Roll vs Double Roll Explained

This confuses everyone, even experienced installers.

The Confusing Part

Wallpaper is priced by the single roll but sold by the double roll. When you see “$40 per roll,” that’s the price per single roll, but you can only buy it in double-roll bolts.

Example:

• Price: $40 per single roll
• You calculate you need 12 rolls
• You order: 6 double-roll bolts at $80 each, which equals $480 total
• What you receive: 6 bolts, each containing 54 feet, which equals 12 single rolls’ worth of coverage

Why This System Exists

Double rolls reduce waste because longer continuous strips mean:

• Fewer seams to match
• Less trimming at ceiling and baseboard
• Better chance of matching patterns across adjacent strips

A 54-foot double roll gives you two full 8-foot strips plus extra for matching, whereas two separate 27-foot single rolls would require opening both and potentially wasting ends.

How to Order Correctly

1. Calculate rolls needed using single-roll coverage (27 sq ft usable)
2. If you need an odd number like 11 rolls, round up to 12 because double rolls come in pairs
3. Order half that number in double-roll bolts, so 12 single rolls equals 6 double rolls
4. Verify the seller is listing double-roll pricing versus single-roll pricing

Red flag: If a seller advertises “single rolls available,” confirm they’re not cutting double rolls in half, which defeats the waste-reduction benefit.

Pattern Repeat and Waste Calculation

Pattern repeat is the distance between where a design element repeats vertically on the roll. This is the single biggest waste factor in wallpaper installation.

What Is Pattern Repeat?

Pattern repeat (also called “vertical repeat”) is measured in inches and printed on every roll’s label.

Example:

• Pattern repeat: 21 inches
• Meaning: Every 21 inches vertically, the design pattern repeats
• Impact: Each strip must be cut to align the pattern, which creates waste

Pattern Repeat Categories

Repeat Size	Waste Factor	Usable Coverage per Single Roll
No repeat (random)	5% waste	30 sq ft
Small repeat (1–12 inches)	10–15% waste	27 sq ft
Medium repeat (13–18 inches)	15–20% waste	25 sq ft
Large repeat (19–24 inches)	20–25% waste	24 sq ft
Extra-large repeat (25+ inches)	25–30% waste	22 sq ft

Formula for waste percentage:

\text{Waste %} = \frac{\text{Pattern Repeat}}{\text{Wall Height}} \times 100

Example: 21-inch repeat on 96-inch wall height equals 21.9% waste.

Straight Match vs Drop Match Patterns

How the pattern aligns horizontally affects cutting and waste.

Straight Match (Straight Across Match)

Definition: The pattern aligns horizontally at the same level across adjacent strips.

Visual: If there’s a flower at 12 inches from the ceiling on strip 1, strip 2 also has a flower at 12 inches.

Waste: Lower waste because all strips are cut identically.

Best for: Stripes, geometric patterns, horizontal designs.

Drop Match (Offset Match or Half-Drop)

Definition: The pattern on strip 2 is offset vertically by half the pattern repeat compared to strip 1.

Visual: If there’s a flower at 12 inches on strip 1, strip 2 has a flower at 23 inches, which equals 12 inches plus half of a 21-inch repeat.

Waste: Higher waste because you alternate between two different cutting patterns.

Best for: Diagonal patterns, brick layouts, organic designs.

Impact: Drop match patterns require 15% to 20% more wallpaper than straight match patterns of the same repeat size.

Calculating Pattern Repeat Waste

Step 1: Determine strips per roll.

$\text{Strips per Roll} = \left\lfloor \frac{\text{Roll Length}}{\text{Wall Height} + \text{Pattern Repeat}} \right\rfloor$

Example: 27-foot roll (324 inches), 8-foot wall (96 inches), 21-inch repeat:

$\text{Strips} = \left\lfloor \frac{324}{96 + 21} \right\rfloor = \left\lfloor 2.77 \right\rfloor = 2 \ \text{strips}$

Step 2: Calculate usable coverage.

$\text{Usable Coverage} = \text{Strips per Roll} \times \text{Wall Height} \times \text{Roll Width}$

$= 2 \times 8 \ \text{ft} \times 2.25 \ \text{ft} = 36 \ \text{sq ft}$

Wait, that’s 36 sq ft, not 27 sq ft. What gives?

Step 3: Apply real-world waste factors.

The theoretical calculation doesn’t account for:

• Trimming top and bottom for ceiling/baseboard gaps
• Damaged edges on the roll
• Corners requiring custom cuts
• Mistakes during installation

Professional installers use 25 to 30 sq ft usable coverage per single roll as a safe estimate regardless of theoretical calculations.

Measuring Rooms with Doors and Windows

Accurate room measurement prevents costly ordering mistakes.

Step 1: Measure Wall Perimeter

Use a tape measure to measure each wall at baseboard level, which is more accurate than assuming rooms are perfectly rectangular.

For rectangular rooms:

• Measure length of one long wall
• Measure length of one short wall
• Perimeter = 2 × (length + width)

For irregular rooms:

• Measure each wall individually
• Add all measurements together

Example: L-shaped room with walls of 12 ft, 8 ft, 6 ft, 4 ft, 6 ft, and 12 ft equals 48 ft perimeter.

Step 2: Measure Ceiling Height

Measure from baseboard top to ceiling, not floor to ceiling.

Why: You’re not wallpapering the baseboard or crown molding.

Multiple measurements: Measure in 3 corners because ceilings are rarely perfectly level. Use the highest measurement to avoid running short.

Step 3: Calculate Wall Area

$\text{Wall Area} = \text{Perimeter} \times \text{Height}$

Example: 44 ft perimeter × 8 ft height = 352 sq ft.

Step 4: Measure Openings (Doors and Windows)

Standard door: 3 ft wide × 7 ft tall = 21 sq ft

Standard window: 3 ft wide × 5 ft tall = 15 sq ft

Large window or patio door: Measure actual dimensions.

Step 5: Subtract Openings

$\text{Net Wall Area} = \text{Gross Wall Area} - \text{Total Openings}$

Example: 352 sq ft - (1 door × 21 sq ft) - (2 windows × 15 sq ft) = 301 sq ft.

Should You Subtract Openings?

Subtract openings if:

• Room has 3 or more large windows
• Room has patio doors or French doors
• Total opening area exceeds 60 sq ft

Don’t subtract openings if:

• Room has only 1 door and 1 small window
• You’re wallpapering around windows (not above/below)
• Pattern repeat is large, which means more waste anyway

Professional tip: Many installers don’t subtract openings under 50 sq ft total because the “saved” wallpaper gets used for mistakes, corners, and obstacles like outlets and light switches.

Ordering Strategy for Dye Lots and Extras

Wallpaper batches vary in color, which creates visible mismatches.

What Is a Dye Lot?

Dye lot (also called “run number” or “batch number”) is a code printed on the roll label indicating when and where the wallpaper was printed.

Example label:

Pattern: Floral Damask
Color: Ivory
Dye Lot: 2408-B
Roll: Double Roll 27" × 54'

The problem: Different dye lots of the same pattern and color can have slight variations in hue, saturation, or pattern alignment due to:

• Different ink batches at the factory
• Printer calibration changes
• Paper substrate variations

The result: A room wallpapered with mixed dye lots will show visible color shifts under natural light, especially where strips from different lots meet.

How to Ensure Same Dye Lot

1. Order all rolls at once

Don’t order 8 rolls now and 4 rolls next week. Order all 12 rolls in one transaction to guarantee they’re pulled from the same production batch.

2. Verify dye lot before installation

When your order arrives, check the dye lot code on every roll before cutting. If one roll has a different code, contact the seller immediately for a replacement.

3. Request same-lot guarantee

When ordering, add a note: “Please ship all rolls from the same dye lot.” Reputable sellers will honor this.

4. Buy from a single source

Don’t split an order between two retailers. They may stock different batches.

How Many Extra Rolls to Order?

Standard recommendation: Add 1 extra roll for every 6 rolls calculated.

Example: If your math says 12 rolls, order 14 rolls (12 + 2 extra).

Why you need extras:

Reason	Likelihood	Rolls Needed
Installation mistakes	70%	0.5 to 1 roll
Pattern matching errors	50%	0.5 roll
Damaged sections of roll	30%	0.25 roll
Future repairs from damage	80% over 5 years	1 roll
Corner/obstacle waste	60%	0.5 roll

Total buffer: 2 to 3 extra rolls for a typical 12-roll room.

What to do with leftovers:

• Store one full roll for future repairs like patching torn sections or replacing damaged areas
• Return unopened rolls if the seller accepts returns, which some do within 30 days
• Keep partial rolls for small projects such as lining drawers or backing shelves

Don’t scrimp on extras. Reordering later risks getting a different dye lot, which will look mismatched even if it’s the same pattern name.

Handling Corners and Obstacles

Real rooms have corners, outlets, switches, and other obstacles that require extra wallpaper.

Inside Corners

Method: Overlap the wallpaper by 1/2 inch on the adjacent wall and trim.

Waste: 1/2 inch per corner × 4 corners = 2 inches of width wasted.

Impact: Minimal, but adds up in rooms with many corners or alcoves.

Outside Corners

Method: Wrap wallpaper around the corner by 1 inch, then start a new strip on the adjacent wall.

Waste: 1 inch per outside corner.

Common locations: Column wraps, chimney projections, bay window sides.

Outlets and Switches

Method: Apply wallpaper over the outlet box, then cut an X from corner to corner and trim excess.

Waste: Negligible, but the cutouts create unusable scrap.

Tip: Turn off power and remove outlet covers before wallpapering. Replace covers after wallpaper dries.

Light Fixtures and Vents

Method: Cut a hole slightly smaller than the fixture, then slip the wallpaper over it.

Waste: The center cutout becomes scrap.

Tip: For ceiling fixtures, make a star-pattern cut from the center outward, then trim after the wallpaper is positioned.

Arches and Curved Walls

Method: Cut multiple narrow strips and overlap them slightly to follow the curve.

Waste: High, because standard strips can’t bend around curves without wrinkling.

Extra rolls: Add 2 to 3 extra rolls for rooms with arches or curved walls.

Coverage by Room Type

Different rooms have different wallpaper needs based on size, openings, and obstacles.

Small Bathroom (5×7 feet, 8 ft ceiling)

• Perimeter: 24 ft
• Wall area: 192 sq ft
• Openings: 1 door at 21 sq ft, 1 window at 15 sq ft
• Net area: 156 sq ft
• Rolls needed (27 sq ft usable per roll): 6 to 7 rolls
• Obstacles: Toilet, sink, mirror, medicine cabinet create extra waste
• Order: 8 rolls (7 + 1 extra)

Standard Bedroom (12×12 feet, 8 ft ceiling)

• Perimeter: 48 ft
• Wall area: 384 sq ft
• Openings: 1 door at 21 sq ft, 2 windows at 15 sq ft each
• Net area: 333 sq ft
• Rolls needed: 12 to 13 rolls
• Order: 14 rolls (13 + 1 extra)

Living Room (18×15 feet, 9 ft ceiling)

• Perimeter: 66 ft
• Wall area: 594 sq ft
• Openings: 2 doors at 21 sq ft each, 3 windows at 15 sq ft each
• Net area: 507 sq ft
• Rolls needed: 19 to 20 rolls
• Obstacles: Fireplace, built-in shelves add complexity
• Order: 22 rolls (20 + 2 extra)

Dining Room (14×12 feet, 8 ft ceiling)

• Perimeter: 52 ft
• Wall area: 416 sq ft
• Openings: 1 door at 21 sq ft, 1 large window at 25 sq ft
• Net area: 370 sq ft
• Rolls needed: 14 to 15 rolls
• Order: 16 rolls (15 + 1 extra)

Hallway (20 feet long × 4 feet wide, 8 ft ceiling)

• Perimeter: 48 ft
• Wall area: 384 sq ft
• Openings: 3 doors at 21 sq ft each
• Net area: 321 sq ft
• Rolls needed: 12 rolls
• Note: Hallways have many corners and doors, which create extra waste
• Order: 14 rolls (12 + 2 extra)

Pro Tips from Professional Installers

1. Number Your Rolls in Installation Order

Before cutting, lay out all rolls and number them 1, 2, 3, etc. in the order you’ll hang them.

Why: If there’s slight color variation between rolls (even in the same dye lot), progressive installation hides it better than random installation.

Method: Start in the least-visible corner and work toward the most-visible wall (usually opposite the entry door).

2. Always Start with a Plumb Line

Walls are never perfectly vertical. Use a level and pencil to mark a true vertical line before hanging the first strip.

Why: If your first strip is crooked, every subsequent strip will be crooked, and the error compounds across the room.

Tool: Use a 4-foot level or a plumb bob, not a laser level, which can be inaccurate on textured walls.

3. Match Seams at Eye Level, Not Ceiling

Pattern matching is most critical at eye level (roughly 5 feet from the floor), because that’s where people notice misalignment.

Priority:

1. Eye-level alignment (5 ft)
2. Baseboard alignment (0 ft)
3. Ceiling alignment (8 ft)

Why: Slight mismatches at the ceiling are less visible than mismatches at eye level.

4. Cut Strips Longest to Shortest

Cut all your strips from longest to shortest, using the longest pieces for full walls and saving shorter pieces for above doors or below windows.

Why: This minimizes waste and ensures you don’t run short on long strips at the end of the job.

5. Overlap Seams by 1/32 Inch, Then Trim

Don’t try to butt seams perfectly. Instead, overlap by a hair, then use a straight edge and razor to cut through both layers and remove the excess.

Result: Perfectly aligned seams with no gaps.

Tool: Use a 6-inch broad knife as a straight edge and a fresh razor blade for every 3 to 4 cuts.

6. Roll Seams, Don’t Press Them

After hanging two adjacent strips, use a seam roller (a small wooden or plastic roller) to gently press the seam flat.

Pressure: Light pressure only. Heavy pressure squeezes out adhesive and creates weak seams.

Timing: Roll seams 5 to 10 minutes after hanging, when the adhesive is still wet but the wallpaper has relaxed.

Common Wallpaper Ordering Mistakes

1. Using Gross Coverage Instead of Usable Coverage

Mistake: “A single roll is 60.75 sq ft, and my room is 360 sq ft, so I need 6 rolls.”

Reality: Usable coverage is 25 to 30 sq ft per roll after pattern repeat waste, so you actually need 12 to 14 rolls.

Fix: Always use 27 sq ft usable coverage for American single rolls with medium pattern repeat.

2. Forgetting Pattern Repeat Exists

Mistake: Ordering based on square footage alone without checking the pattern repeat size.

Reality: A 24-inch repeat wastes 25% more wallpaper than a 12-inch repeat.

Fix: Check the pattern repeat on the label before calculating. Adjust usable coverage down for large repeats.

3. Ordering Single Rolls When Only Double Rolls Are Sold

Mistake: “I need 11 rolls, so I’ll order 11 single rolls.”

Reality: Wallpaper is sold in double-roll bolts, so you’ll receive 6 bolts, which equals 12 single rolls’ worth of coverage.

Fix: Calculate in single-roll units, then order half that number in double-roll bolts. Round up to the next even number.

4. Splitting Orders Across Multiple Purchases

Mistake: Ordering 8 rolls now and 4 rolls next month when the project expands.

Reality: The second order will likely come from a different dye lot, creating visible color mismatches.

Fix: Order all wallpaper for connected rooms at once, even if you’re installing in phases.

5. Not Accounting for Ceiling Height Differences

Mistake: Assuming all rooms have 8-foot ceilings and ordering based on that.

Reality: Older homes often have 9-foot or 10-foot ceilings, which require 25% more wallpaper.

Fix: Measure actual ceiling height in each room. Don’t assume.

6. Subtracting Too Many Openings

Mistake: Subtracting every door and window to “save money.”

Reality: The wallpaper you “save” by subtracting openings gets used for:

• Cutting around outlets and switches
• Trimming corners
• Fixing mistakes
• Pattern matching waste

Fix: Only subtract openings if total opening area exceeds 60 sq ft. Otherwise, use gross wall area.

7. Trusting Online Calculators Blindly

Mistake: Using a free online calculator that doesn’t ask about pattern repeat, dye lot, or room complexity.

Reality: Generic calculators underestimate by 10% to 20% because they assume perfect installation and no waste.

Fix: Use a calculator that asks for pattern repeat, then add 1 to 2 extra rolls manually.

Wallpaper Types and Coverage Differences

Not all wallpaper has the same coverage rate. Material and backing affect waste.

Vinyl Wallpaper (Standard Coverage)

Material: PVC coating on paper or fabric backing.

Coverage: 25 to 30 sq ft usable per single roll.

Waste factor: Standard, because vinyl is forgiving and stretches slightly.

Best for: Kitchens, bathrooms, high-traffic areas because it’s washable.

Non-Woven Wallpaper (Higher Coverage)

Material: Synthetic fibers (polyester, cellulose) without a paper backing.

Coverage: 28 to 32 sq ft usable per single roll.

Waste factor: Lower, because non-woven doesn’t shrink or expand when wet.

Best for: DIY installation because it’s easier to hang and remove.

Bonus: Paste-the-wall application, so you don’t need to paste the wallpaper itself.

Grasscloth and Natural Fiber (Lower Coverage)

Material: Real grass, bamboo, cork, or wood veneer on paper backing.

Coverage: 20 to 25 sq ft usable per single roll.

Waste factor: Higher, because natural fibers have grain direction and color variation that require careful matching.

Best for: Accent walls because it’s expensive and difficult to install.

Warning: Seams are visible due to material texture. Plan seam placement carefully.

Foil and Metallic Wallpaper (Lower Coverage)

Material: Metallic film on paper backing.

Coverage: 22 to 27 sq ft usable per single roll.

Waste factor: Higher, because foil shows every imperfection and requires perfect wall prep.

Best for: Small accent areas because it’s reflective and shows flaws.

Tip: Prime walls with metallic wallpaper primer to prevent tarnishing.

Paintable Wallpaper (Standard Coverage)

Material: Textured paper or vinyl designed to be painted after installation.

Coverage: 25 to 30 sq ft usable per single roll.

Waste factor: Standard, but you’ll use extra paint to cover the texture.

Best for: Disguising wall imperfections while adding texture.

Frequently Asked Questions

How many rolls of wallpaper do I need for a 12x12 room?

For a 12×12 room with 8-foot ceilings, you need approximately 12 to 14 single rolls (6 to 7 double rolls). The exact number depends on pattern repeat size and the number of doors and windows. Wall area is roughly 384 square feet, which equals a 48-foot perimeter times an 8-foot height. After subtracting one door and two windows, you have about 333 sq ft of net wall area. At 27 sq ft usable coverage per single roll, you need 12.3 rolls. Always round up and add 1 extra roll for mistakes and future repairs, so order 14 single rolls or 7 double-roll bolts.

What is the difference between a single roll and double roll?

A single roll is 27 inches wide by 27 feet long with 60.75 sq ft of gross coverage. A double roll is 27 inches wide by 54 feet long with 121.5 sq ft of gross coverage. Wallpaper is priced per single roll but sold in double-roll bolts because longer strips reduce waste and create fewer seams. If you calculate you need 11 single rolls, you must order 6 double-roll bolts, which gives you 12 single rolls’ worth of coverage. You can’t buy a single roll by itself because manufacturers package wallpaper in double-roll bolts.

How do I calculate pattern repeat waste?

Pattern repeat waste depends on the repeat size and your wall height. The formula is: strips per roll equals roll length divided by wall height plus pattern repeat, rounded down. For a 27-foot roll, 8-foot wall, and 21-inch repeat, you get 2 strips per roll instead of 3. This reduces usable coverage from 60.75 sq ft to about 36 sq ft theoretical, but real-world waste brings it down to 25 to 30 sq ft usable per roll. Always use 27 sq ft as a safe estimate for medium pattern repeats.

Should I subtract doors and windows when calculating wallpaper?

Subtract doors and windows only if total opening area exceeds 60 sq ft. For most rooms with one door and two windows, the 51 sq ft of openings saves only 1.9 rolls, but that wallpaper gets used for corner cuts, outlet trimming, and pattern matching waste. Professional installers don’t subtract openings in rooms under 400 sq ft because the math savings disappear in real-world installation. For large rooms over 500 sq ft with multiple patio doors or large windows, subtract openings to avoid buying an extra 2 to 3 rolls.

What happens if I order wallpaper from different dye lots?

Different dye lots will have slight color variations that are invisible when you hold two rolls side by side but become obvious when installed on the wall under natural light. The color shift will appear as a visible line where strips from different lots meet. This can’t be fixed without removing and replacing the wallpaper. Always order all rolls at once from the same retailer and verify every roll has the same dye lot number on the label before installation. If one roll has a different code, contact the seller for a replacement before cutting any wallpaper.

How many extra rolls should I order for mistakes and repairs?

Add 1 extra roll for every 6 rolls calculated, which equals roughly 15% to 20% buffer. For a 12-roll calculation, order 14 rolls. This covers installation mistakes like pattern misalignment, damaged sections on the roll, corner and obstacle waste, and future repairs from wall damage over the next 5 to 10 years. Store at least one full unopened roll in a cool, dry place for future patching. You can’t buy more of the same dye lot later, so extras are insurance against running short mid-project or needing repairs years later.

Use our wallpaper calculator to calculate exact rolls needed based on your room dimensions, pattern repeat, and wallpaper type. The calculator accounts for pattern waste, rounds to the nearest double-roll bolt, and adds the recommended buffer for mistakes and repairs.