Ideal Weight Calculator

How this calculator works

Enter your height and sex and the ideal weight calculator returns five numbers, not one. Four come from the classic ideal body weight (IBW) formulas: Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964). The fifth is a range, the span of weights that puts your body mass index between 18.5 and 24.9, the band the CDC and NIH call a healthy weight.

All four formulas share one shape: a base weight at 5 feet tall, plus a fixed amount for every inch above that. Devine gives a man 50 kg plus 2.3 kg per inch over 5 feet, a woman 45.5 kg plus 2.3 kg per inch. Hamwi is the one most Americans hear from a dietitian: 100 lb for the first 5 feet plus 5 lb per inch for women, 106 lb plus 6 lb per inch for men.

Here is the part most ideal weight charts leave out. These equations were never built to tell you how you should look. Pharmacists needed a quick estimate of body size to dose drugs such as gentamicin, and Devine's 1974 formula was written for that. When Pai and Paloucek traced the origins in 2000, they found the numbers came from insurance height-weight tables, not from any study of health outcomes. Hamwi's version came from a 1964 diabetes handbook; Robinson and Miller reworked the tables in 1983. None of them measured body fat, fitness or lifespan. The BMI range under the formulas is the only line tied to health data, which is why we show it every time.

How to read your result

Expect the four formulas to disagree by 5 to 15 lb, with the gap widening the further you are from 5 feet. A 5'4" woman gets about 121 lb from Devine, 123 lb from Robinson, 129 lb from Miller and 120 lb from Hamwi. Her healthy BMI range runs 108 to 145 lb. That spread is the honest answer: every weight inside it is defensible.

Hamwi also allowed a frame adjustment: about 10 percent off for a small frame, 10 percent on for a large one. The calculator shows the base number; shift it yourself if your wrist is clearly slim or broad for your height.

Healthy BMI weight range by height

The range is the same for women and men because BMI does not use sex. The NIH BMI table extends it to every inch from 4'10" to 6'4".

Where the number misleads

Frame and bone. Two women at 5'6" can differ by 10 to 15 lb of skeleton before a single ounce of fat enters the picture. The formulas assume an average frame.

Muscle. IBW equations and BMI weigh muscle and fat the same. A woman who lifts twice a week can "fail" Devine while being leaner than a neighbor who passes it.

Age. After 65 the picture shifts. In a 2014 meta-analysis of 32 studies in older adults, the lowest death rate sat at a BMI in the mid-20s to about 30, and risk rose once BMI dropped below 23. Weight lost late in life is often muscle, so a "perfect" number from a 1974 formula can be a warning sign at 72 rather than a goal.

Body composition. None of the five numbers know where your weight sits. Waist size tracks metabolic risk better than the scale; over 35 inches for women or 40 inches for men is the CDC threshold worth acting on, whatever the ideal body weight formulas say.

Pregnancy, fluid, medication. Weight from pregnancy, swelling, or drugs such as steroids belongs in a conversation with your clinician, not in a formula.

This is why a range beats a single number. One "ideal weight for height" invites you to chase 3 lb that do not matter. A 35-lb healthy range lets you settle where your energy, blood pressure and bloodwork look best.

What to do with it

1. Write down the range, not the formulas. Note where you sit in the healthy BMI span today and revisit it in three months.
2. Measure your waist once a month. Tape at the navel, relaxed exhale, same time of day. If the waist shrinks while the scale barely moves, you are trading fat for muscle, which is the outcome you want.
3. If you are above the range, start with protein and walking, not a crash diet. A protein-heavy breakfast takes the edge off afternoon cravings, and a 10-minute walk after meals flattens the post-meal blood sugar rise. Both protect muscle while weight comes down.
4. If you are over 65 and near the bottom of the range, protect your weight. Ask for a grip-strength and gait check at your next physical; our retirement checklist for your body lists which screenings to request and when.
5. Take a surprising result to a clinician. Far outside the range in either direction, or 10 lb moved without trying, deserves bloodwork and a conversation, not another formula.