Ideal weight calculator
Your height runs through the four formulas clinicians actually use, side by side, so you get a range rather than one number pretending to be the truth.
Current weight is only used to show how far you sit from the healthy BMI range. Leave it blank if you would rather not.
The four formulas, one row each
Devine · Robinson · Miller · Hamwi| Formula | Ideal weight |
|---|
Three of these four were written for pharmacists working out drug doses, not for anyone deciding what to weigh. The healthy BMI range is the only line in this table that comes from health outcomes.
How we got your number
Devine 1974, Robinson 1983, Miller 1983 and Hamwi 1964, computed exactly as published. The BMI band uses the WHO cut-offs of 18.5 and 24.9.
Note: all four formulas were only defined for heights of 5 ft and above. Below that they are being extended downwards, which their authors never tested. Read the BMI range instead.
Why formulas from the 1960s and 1970s give women lower numbers
Look at the bases. Devine starts a man at 50.0 kg and a woman at 45.5 kg for the same five feet of height. Robinson widens the gap in the slope as well: 1.9 kg per inch for men against 1.7 for women. Hamwi is the starkest, 2.7 against 2.2. Nothing in physiology produced those gaps. They were reverse engineered from the Metropolitan Life Insurance tables of desirable weight, which were assembled from policyholders who had been medically examined between the 1930s and the 1950s. That sample was mostly white, mostly urban, mostly people who could afford life insurance, and the female half of it was smaller and more weakly sampled than the male half.
Miller, in 1983, refitted the whole thing and came out with a much flatter female slope of 1.36 kg per inch against Hamwi's 2.2. At 185 cm those two differ by about three kilos for a woman and by more than eight for a man, and for women they cross over at around 175 cm, so a woman just below that height gets a higher number from Miller and a woman just above it gets a higher number from Hamwi. Equations that swap places like that are not measuring anything real. The female half of all four is the part built on the thinnest data, and it is the part that has been redrawn most often.
Why ideal weight is the wrong question
A weight is one number that lumps together bone, muscle, fat, water and whatever you last drank. Two people at the same height and the same weight can have completely different amounts of each, and the health risk sits with the composition, not the total. This is why the formulas above can only ever be a rough bracket.
Three measurements do more work than any target weight:
- Waist circumference. Measured at the midpoint between the lowest rib and the top of the hip bone. Risk starts rising above 94 cm for men and 80 cm for women, and is clearly raised above 102 cm and 88 cm. A waist under half your height is the simplest version of the same rule.
- Strength and how you move. If your squat, your carry or your stairs are getting easier, you are gaining or keeping muscle. That shows up as no change on the scale while the body underneath changes a great deal.
- Blood markers. Fasting glucose or HbA1c, blood pressure, and the triglyceride to HDL picture. These move on a diet change within weeks and they are what the weight was standing in for all along.
If every one of those looks good, a weight above your Devine number is not a problem to solve.
What the four formulas are actually used for
In hospitals, ideal body weight is still calculated daily, and almost never to advise a patient. It sets the dose of drugs that distribute poorly into fat tissue, so a 140 kg patient does not get an aminoglycoside dose calculated on all 140 kg. It sets tidal volume on a ventilator, where the standard of 6 to 8 ml per kilogram of predicted body weight uses a height based equation for exactly this reason. It sets the denominator for creatinine clearance estimates.
That is the job these equations do well. Telling a healthy adult what to weigh is a job nobody ever asked them to do, and they were never tested at it.
The four formulas are Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964), the ones used in clinical dosing and dietetics. The healthy range follows the WHO BMI band of 18.5 to 24.9. Nothing you enter is stored or sent anywhere. How we verify our data →
Ideal weight FAQs
What is my ideal weight?
For a 170 cm woman the four formulas give 57 to 62 kg; for a man of the same height 63 to 66 kg. The healthy BMI band for that height is wider, 53.5 to 72 kg, and any weight inside it is fine for health.
Which ideal weight formula is most accurate?
None is more accurate than the others, because none was designed to find your best weight. Devine was written for drug dosing, Hamwi for quick clinic estimates. Treat the four as a range and the BMI band as the limit.
Is ideal weight the same as healthy weight?
No. Ideal weight is a single point from a formula. Healthy weight is the whole BMI range from 18.5 to 24.9 for your height, and it is about 18 kg wide for an average adult.
Does ideal weight depend on age?
The formulas ignore age, and so do the WHO thresholds. From about 65 onwards a slightly higher weight, BMI 23 to 27, is linked with better outcomes, mostly because it protects against muscle loss.
Does frame size change ideal weight?
By roughly 10 percent. A large frame, judged by wrist or elbow width, sits at the top of the range, a small frame at the bottom. Frame size is a fair reason to be 5 kg above a formula number, not 20.
Why do the four formulas disagree?
They were fitted to different groups in different decades. Devine and Hamwi come from the 1960s and 1970s and give women noticeably lower numbers; Robinson and Miller were refits ten years later. A spread of 5 to 8 kg between them is normal.
