Search “ideal weight” and you will find a dozen different calculators giving different answers for the same person. The disagreement is not a bug — it is because “ideal weight” has no single definition, and the five classical formulas were developed for different purposes at different times for different populations. Understanding what each one represents helps you pick the right target, or recognize that there is no single right target at all.

The five classical formulas

Each formula takes height and returns a target weight in kilograms. All are for adults.

Devine (1974)

  • Men: 50 kg + 2.3 kg per inch over 60 inches
  • Women: 45.5 kg + 2.3 kg per inch over 60 inches

Originally developed by pharmacist B.J. Devine for pharmaceutical dosing — ensuring the “right” dose based on a lean body mass estimate. Still widely used in clinical medicine for drug dosing calculations. Tends to give slightly low numbers for tall people.

Robinson (1983)

  • Men: 52 kg + 1.9 kg per inch over 60 inches
  • Women: 49 kg + 1.7 kg per inch over 60 inches

A correction to Devine based on updated US population data. Generally gives higher weights than Devine, especially for taller individuals.

Miller (1983)

  • Men: 56.2 kg + 1.41 kg per inch over 60 inches
  • Women: 53.1 kg + 1.36 kg per inch over 60 inches

Another clinical formula, giving higher base weights but smaller per-inch adjustments. Tends to compress the spread between short and tall people.

Hamwi (1964)

  • Men: 48 kg + 2.7 kg per inch over 60 inches
  • Women: 45.5 kg + 2.2 kg per inch over 60 inches

The oldest of the four, developed for diabetic dietary planning. Still widely used in nutrition and clinical dietetics.

BMI-based healthy range

Any weight that puts the person in BMI 18.5-24.9. This gives a range rather than a single number: for a 5’10” adult, that is 129-173 lb. The range approach is often more useful than the single-point formulas.

A worked example: 5’10” man

Height: 70 inches = 10 inches over 60.

  • Devine: 50 + (2.3 × 10) = 73 kg = 161 lb
  • Robinson: 52 + (1.9 × 10) = 71 kg = 157 lb
  • Miller: 56.2 + (1.41 × 10) = 70.3 kg = 155 lb
  • Hamwi: 48 + (2.7 × 10) = 75 kg = 165 lb
  • BMI range: 129-173 lb

Four different answers spanning 10 pounds — and the BMI range swallows all of them plus considerable margin on either side. For a 5’4” woman: Devine 54.7 kg (120 lb), Robinson 55.8 kg (123 lb), Miller 58.5 kg (129 lb), Hamwi 54.3 kg (120 lb). BMI range 108-145 lb.

What each formula is for

Devine and Hamwi are clinical formulas used in medicine for drug dosing, parenteral nutrition, and body composition estimates in specific medical contexts. They are not lifestyle targets.

Robinson and Miller are also clinical but reflect later population data. They tend to give higher numbers that may better approximate the real lean body mass of average US adults.

BMI range is what public health uses. It defines a zone where mortality risk is lowest at the population level. Any weight inside the range is considered healthy — the specific number within the range is a personal matter.

None of these formulas account for:

  • Muscle mass (a muscular person has higher ideal weight)
  • Frame size (large-framed people have higher ideal weight)
  • Age (ideal weight may shift slightly up with age)
  • Ethnicity (population body composition varies)
  • Fitness level (not reflected at all)

Frame size adjustments

The easiest way to check frame size: measure wrist circumference at its narrowest. For men: under 5.5 inches = small frame; 5.5-6.5 = medium; over 6.5 = large. For women: under 5.75 inches = small, over 6.25 = large. Adjust the calculated “ideal” by ±10% up for large frames and down for small frames.

A 5’10” man with a large frame has an “ideal” of roughly 165-180 lb (higher end of the BMI range plus frame adjustment). The same height man with a small frame is closer to 140-155 lb.

Another quick test: with your dominant hand, circle your opposite wrist with thumb and middle finger. Thumb overlaps middle finger = small frame. Thumb touches middle finger = medium. Does not reach = large.

The “ideal weight” problem

Modern sports and nutrition science has largely moved away from the single “ideal weight” concept toward body composition targets. Whether you are 165 or 180 lb matters less than whether the composition of that weight is 15% fat and high lean mass vs 30% fat and low lean mass.

That said, ideal weight formulas still have real uses:

  • Sanity-checking a goal. If you are 6’0” and targeting 130 lb, every formula agrees this is too low.
  • Medical dosing and nutritional planning in clinical settings.
  • Screening for malnutrition and obesity on basic assessments.
  • Setting realistic expectations during weight loss. “Losing 40 pounds” means different things at different starting points.

A practical approach

For most healthy adults trying to set a goal weight:

  1. Calculate your BMI range (18.5 to 24.9 × height in meters2). This is your healthy zone.
  2. Within that zone, pick a specific number. Medium-framed, moderately active adults often aim near BMI 22-24. Very active or muscular people aim higher.
  3. Check against a body composition target rather than just weight — a leaner body at slightly higher weight is better than a flabbier body at the “ideal” weight.
  4. Iterate. Actual maintenance weight tends to settle 5-10 pounds higher or lower than predicted depending on your real metabolism and preferences.

When to ignore the formulas entirely

  • You are significantly above or below average height (under 5’0” or over 6’5”). Formulas extrapolate poorly here.
  • You are very muscular. Your ideal weight is well above BMI 25.
  • You are over 65. A slightly higher weight (BMI 24-28) is associated with lower mortality in older adults.
  • You are pregnant or postpartum. Consult weight guidelines appropriate to that life stage.
  • You have an eating disorder history. Defer to medical guidance, not calculators.

Find your range

Our ideal weight calculator returns all five formulas plus the BMI range, giving you a full picture. Use the range as guidance, frame-adjust based on your wrist, and plan for a target somewhere near the middle of your BMI-healthy range unless you have specific reasons to aim higher or lower. The goal is a weight you can reach and maintain while keeping the body composition you want — which is rarely exactly what any 1970s formula predicted.