How to Calculate Ideal Weight (4 Formulas Compared)

The concept of “ideal weight” has been around since the 1800s when life insurance companies started linking body weight to mortality risk. Today, four formulas are commonly used to estimate ideal body weight (IBW), each developed by different researchers with slightly different assumptions. None of them are perfect, but understanding how they work helps you interpret the numbers and set realistic goals.

This guide compares all four formulas side by side, shows you the math with worked examples, and explains why your ideal weight depends on more than just height. For quick results across all formulas, use our Ideal Weight Calculator.

Medical Disclaimer: Ideal body weight formulas are simplified estimates originally developed for clinical purposes like drug dosing, not as definitive health targets. Your healthy weight depends on body composition, genetics, age, fitness level, and medical history. Consult a healthcare provider or registered dietitian for personalized weight guidance.

The Four Major Formulas

All four formulas share the same basic structure: they start with a base weight for 5 feet of height (60 inches) and add a fixed amount per additional inch. The formulas differ in their base values and per-inch increments, which is why they produce different results.

1. Devine Formula (1974)

Dr. B.J. Devine published this formula for calculating drug dosages based on body weight. It became the most widely used IBW formula in medicine, pharmacology, and nutrition despite being intended for medication dosing rather than health targets.

For men:

$IBW = 50 + 2.3 \times (height_{in} - 60) \quad kg$

For women:

$IBW = 45.5 + 2.3 \times (height_{in} - 60) \quad kg$

2. Robinson Formula (1983)

Dr. J.D. Robinson and colleagues published a revision intended to be more accurate for a broader population than the Devine formula.

For men:

$IBW = 52 + 1.9 \times (height_{in} - 60) \quad kg$

For women:

$IBW = 49 + 1.7 \times (height_{in} - 60) \quad kg$

3. Miller Formula (1983)

Dr. D.R. Miller published this formula in the same year as Robinson. It tends to produce the highest estimates of the four, particularly for taller individuals.

For men:

$IBW = 56.2 + 1.41 \times (height_{in} - 60) \quad kg$

For women:

$IBW = 53.1 + 1.36 \times (height_{in} - 60) \quad kg$

4. Hamwi Formula (1964)

Dr. G.J. Hamwi published the earliest of the four modern formulas. It is still used in some clinical nutrition settings and tends to produce moderate estimates.

For men:

$IBW = 48.0 + 2.7 \times (height_{in} - 60) \quad kg$

For women:

$IBW = 45.5 + 2.2 \times (height_{in} - 60) \quad kg$

Worked Examples: All Four Compared

Male, 5’10” (70 inches)

Formula	Calculation	Result (kg)	Result (lbs)
Devine	50 + 2.3 x (70 - 60)	73.0 kg	161 lbs
Robinson	52 + 1.9 x (70 - 60)	71.0 kg	157 lbs
Miller	56.2 + 1.41 x (70 - 60)	70.3 kg	155 lbs
Hamwi	48.0 + 2.7 x (70 - 60)	75.0 kg	165 lbs

Range: 155-165 lbs. The average across all four is about 159.5 lbs.

Female, 5’5” (65 inches)

Formula	Calculation	Result (kg)	Result (lbs)
Devine	45.5 + 2.3 x (65 - 60)	57.0 kg	126 lbs
Robinson	49 + 1.7 x (65 - 60)	57.5 kg	127 lbs
Miller	53.1 + 1.36 x (65 - 60)	59.9 kg	132 lbs
Hamwi	45.5 + 2.2 x (65 - 60)	56.5 kg	125 lbs

Range: 125-132 lbs. The average across all four is about 127.5 lbs.

Male, 6’2” (74 inches)

Formula	Calculation	Result (kg)	Result (lbs)
Devine	50 + 2.3 x (74 - 60)	82.2 kg	181 lbs
Robinson	52 + 1.9 x (74 - 60)	78.6 kg	173 lbs
Miller	56.2 + 1.41 x (74 - 60)	75.9 kg	167 lbs
Hamwi	48.0 + 2.7 x (74 - 60)	85.8 kg	189 lbs

Range: 167-189 lbs. Notice how the formulas diverge more at taller heights because the per-inch increments differ. The spread is 22 lbs here versus only 10 lbs for the 5’10” male.

The BMI-Based Approach

Instead of a single number, you can calculate a healthy weight range based on the WHO’s normal BMI window of 18.5 to 24.9.

Formula:

$Weight_{min} = 18.5 \times height_{m}^2$ $Weight_{max} = 24.9 \times height_{m}^2$

Example for 5’10” (1.778 m):

• Minimum: 18.5 x (1.778)^2 = 18.5 x 3.161 = 58.5 kg (129 lbs)
• Maximum: 24.9 x (1.778)^2 = 24.9 x 3.161 = 78.7 kg (174 lbs)

This gives a healthy range of 129-174 lbs, which is broader and arguably more realistic than a single target number. The formula-based ideal weights (155-165 lbs for a 5’10” male) fall within this range, sitting at the higher end of the BMI spectrum (roughly BMI 22-24).

Why “Ideal Weight” Varies

Frame Size

Bone structure varies. A person with a large frame (wider shoulders, larger wrists, broader hips) will naturally weigh more than someone of the same height with a small frame, even at the same body fat percentage. The Hamwi method traditionally included frame size adjustments:

• Small frame: Subtract 10% from the IBW result
• Large frame: Add 10% to the IBW result

A rough way to estimate frame size: wrap your thumb and index finger around your wrist. If they overlap, you have a small frame. If they just touch, medium. If they don’t meet, large.

For the 5’10” male using the Hamwi result of 165 lbs:

• Small frame: 165 - 16.5 = 148.5 lbs
• Medium frame: 165 lbs
• Large frame: 165 + 16.5 = 181.5 lbs

Muscle Mass

A person who strength trains regularly carries more muscle, which weighs more than fat by volume. A 5’10” male at 180 lbs with 15% body fat is leaner and healthier than a 5’10” male at 165 lbs with 28% body fat, even though the lighter person is closer to the “ideal” number.

This is the fundamental limitation of any height-based weight formula: it can’t account for what your weight is made of.

Age

Body composition shifts with age. Lean mass tends to decrease while fat mass increases, even if total weight stays constant. An appropriate weight for a 25-year-old athlete may be different from what serves a 65-year-old retiree best. Some research suggests that slightly higher BMI values (25-27) are associated with the lowest mortality risk in adults over 65, challenging the standard cutoffs.

Sex

The formulas already account for sex with different base values, but within each sex, individual variation is enormous. Hormonal profiles, genetic predisposition for muscle or fat storage, and reproductive factors (pregnancy history, menopause) all influence what a healthy weight looks like for a specific person.

Ethnicity

The original formulas were developed primarily using data from Caucasian American and European populations. Body proportions (leg length relative to torso, shoulder width, hip structure) vary across ethnic groups, which affects what weight is appropriate for a given height.

Healthy Weight vs. Aesthetic Goals

It’s worth separating health targets from appearance goals. The healthy weight range based on BMI (18.5-24.9) is wide enough to include people who look very different from each other. A 5’8” woman at 125 lbs and one at 160 lbs can both be within the healthy BMI range and both be medically fine.

Social media, fitness culture, and entertainment often promote body ideals that fall outside the range most people can maintain without extreme restriction. Sustaining 8% body fat year-round or achieving a specific aesthetic requires a level of dietary control and training that’s unrealistic for most lifestyles and may not be medically optimal.

A more practical approach: find the weight range where you feel energetic, sleep well, perform your daily activities without limitation, and your blood markers (cholesterol, blood sugar, blood pressure) are in healthy ranges. That is your personal healthy weight, regardless of what a formula says.

Which Formula Should You Use?

There’s no single correct answer. Here’s a practical decision framework:

• For clinical or pharmacy contexts: Devine is the standard.
• For a moderate, middle-ground estimate: Robinson gives balanced results.
• For a higher estimate that accommodates more muscle: Miller tends to be most generous.
• For a traditional nutrition assessment: Hamwi with frame size adjustment is common in dietetic practice.
• For the most useful approach overall: Calculate all four, then look at the BMI-based healthy range. Your target should fall somewhere within that range based on your body composition and lifestyle.

Our Ideal Weight Calculator runs all four formulas plus the BMI-based range simultaneously, so you can compare results and find the range that makes sense for your situation.

Frequently Asked Questions

Are ideal weight formulas accurate?

They are rough estimates, not precise targets. These formulas were derived from limited population samples decades ago and don’t account for body composition, frame size, ethnicity, or fitness level. Their primary value is providing a general reference point. A 10-15 lb range around any formula result is more realistic than treating the exact number as a hard target. The BMI-based approach (18.5-24.9) gives you the widest validated healthy range.

Why do the four formulas give different results?

Each formula was developed from different study populations using different statistical methods. Devine used limited clinical data for drug dosing. Robinson and Miller both attempted corrections using broader datasets. Hamwi drew from earlier actuarial data. They agree most closely around average heights (5’5” to 5’10”) and diverge more at height extremes because their per-inch increments differ.

Should I aim for my ideal weight or a healthy BMI range?

A healthy BMI range is generally more useful because it gives you a window rather than a single number. Within that window, your optimal weight depends on your personal body composition, activity level, and how you feel and function. Many health professionals have moved away from targeting a specific ideal weight in favor of sustainable habits that let your body settle at its natural healthy weight.

How does frame size affect ideal weight?

Frame size can shift your ideal weight by roughly 10-15%. A person with a large frame (wider bones, broader joints) will naturally weigh more than someone of the same height with a small frame. You can estimate your frame size by measuring your wrist circumference and comparing it to height-based reference charts, or by using the thumb-and-finger wrap test described above. The Hamwi formula traditionally adjusts plus or minus 10% based on frame size.

Is there a different ideal weight for older adults?

Research suggests that the optimal weight range shifts slightly higher with age. Studies on adults over 65 have found that BMI values in the 25-27 range (technically “overweight” by WHO standards) are associated with the lowest mortality risk. This may be because a modest fat reserve provides protection during illness or injury, and because the health risks of being slightly overweight decrease relative to the risks of being underweight as you age. Discuss age-appropriate weight targets with your doctor.