About This Tool
Unit conversion is a fundamental skill used across science, engineering, cooking, travel, and everyday life. Mixing up units has caused costly errors, from miscalculated building materials to the loss of a $125 million Mars orbiter. This unit converter handles seven major categories: length, weight, temperature, volume, speed, area, and digital data storage. Enter a value, pick your source and target units, and get an accurate result instantly. A quick-reference table accompanies each category so you can memorize the most common conversion factors over time. No signup required, no data stored, and all calculations happen in real time as you type.
How to Use This Unit Converter
Start by selecting a category from the buttons at the top. The available "From" and "To" units will update to match your chosen category. Enter the numeric value you want to convert, select the source unit, and select the target unit. The result appears immediately below.
Use the Swap Units button to quickly reverse the direction of conversion. The quick-reference table at the bottom shows the most commonly needed conversion factors for the active category, so you can double-check your results or learn the factors by heart.
The converter supports both metric and imperial units across all categories. For temperature, it handles Fahrenheit, Celsius, and Kelvin with the exact formulas rather than simple multiplication factors. Digital data conversions use binary (base-1024) values, which is the standard used by operating systems and memory manufacturers.
Common Conversion Formulas
Each category uses a specific base unit internally, and all conversions pass through that base. Here are the key relationships:
- Length: 1 inch = 2.54 cm (exact). 1 foot = 12 inches. 1 mile = 5,280 feet = 1,609.344 meters.
- Weight: 1 pound = 453.59237 grams (exact). 1 kilogram = 2.20462 pounds. 1 US ton = 2,000 pounds.
- Temperature: F to C: subtract 32, multiply by 5/9. C to K: add 273.15. These are non-linear, so there is no single multiplication factor.
- Volume: 1 gallon = 3.78541 liters. 1 cup = 236.588 ml. 1 fluid ounce = 29.5735 ml.
- Speed: 1 mph = 1.60934 km/h. 1 knot = 1.852 km/h. 1 m/s = 3.6 km/h.
- Area: 1 acre = 43,560 sq ft = 4,046.86 sq m. 1 hectare = 10,000 sq m = 2.471 acres.
- Data: 1 KB = 1,024 bytes. Each step up (MB, GB, TB, PB) multiplies by 1,024.
Metric vs. Imperial Systems
The metric system (SI) is used by virtually every country except the United States, Liberia, and Myanmar. It is based on powers of 10, making mental math straightforward: 1 kilometer = 1,000 meters, 1 kilogram = 1,000 grams.
The imperial system uses historical units that do not follow a consistent pattern: 12 inches in a foot, 3 feet in a yard, 5,280 feet in a mile. This irregularity makes conversions harder without a calculator.
In practice, many fields use mixed systems. A US construction worker might measure lumber in feet and inches but order concrete in cubic yards. A baker in the UK might use grams for dry ingredients and cups for liquids. This converter handles all these cross-system conversions in a single tool.
Why Accurate Unit Conversion Matters
Incorrect unit conversions have real consequences. NASA lost the Mars Climate Orbiter in 1999 because one engineering team used imperial units while another used metric. The resulting navigation error sent the spacecraft too close to Mars, where it burned up in the atmosphere.
In construction, converting square feet to square meters incorrectly when ordering flooring or roofing material leads to costly over-orders or project delays. In medicine, dosage calculations depend on precise weight conversions between pounds and kilograms. In cooking, converting between cups and milliliters determines whether a recipe turns out correctly or fails.
Using a reliable converter eliminates mental math errors. Always double-check critical conversions, especially in professional contexts where mistakes carry financial or safety implications.
Frequently Asked Questions
What is the difference between metric tons and US tons?
A metric ton (also called a tonne) equals 1,000 kilograms or approximately 2,204.6 pounds. A US ton (short ton) equals 2,000 pounds or approximately 907.2 kilograms. The metric ton is about 10% heavier than the US ton. In shipping and international trade, the metric ton is the global standard. Always clarify which "ton" is meant when reading specifications or contracts.
Why does this converter use 1,024 bytes per kilobyte instead of 1,000?
Computer memory is binary, so storage is measured in powers of 2. One kilobyte equals 2^10 = 1,024 bytes. This convention is used by operating systems, RAM manufacturers, and file systems. Hard drive manufacturers sometimes use 1,000 bytes per kilobyte (decimal) for marketing, which is why a "500 GB" drive shows as roughly 465 GB in your operating system. This converter uses the binary (base-1024) standard since that matches what your computer actually reports.
How do I convert temperature without a calculator?
For a rough Fahrenheit-to-Celsius estimate, subtract 30 and divide by 2. For example, 80 F becomes (80 - 30) / 2 = 25 C (actual: 26.7 C). For Celsius to Fahrenheit, double the value and add 30. So 20 C becomes 20 * 2 + 30 = 70 F (actual: 68 F). These shortcuts are close enough for weather and cooking estimates but not for scientific work.
What is a nautical mile and how does it differ from a regular mile?
A nautical mile equals 1,852 meters (about 1.151 regular miles or 6,076 feet). It was originally defined as one minute of arc along a meridian of the Earth, making it naturally useful for navigation at sea and in aviation. Speed in nautical miles per hour is called "knots." One knot equals 1.852 km/h or approximately 1.151 mph.
How do I convert between acres and square feet?
One acre equals exactly 43,560 square feet. To convert acres to square feet, multiply by 43,560. To convert square feet to acres, divide by 43,560. For context, an American football field (excluding end zones) is about 1.1 acres, and a standard city lot is typically between 0.1 and 0.25 acres depending on the region.
Is a fluid ounce the same as a regular ounce?
No. A fluid ounce measures volume (how much space a liquid takes up), while an ounce measures weight (how heavy something is). One fluid ounce of water weighs approximately one ounce, but this only works for water. One fluid ounce of honey weighs about 1.5 ounces because honey is denser. Always check whether a recipe or specification means fluid ounces (volume) or ounces (weight).