There is no single "ideal weight." There are four main scientific formulas, and they give different answers — sometimes by several kilograms. Here's how each one works and what the difference means.
All four are based on height, with adjustments for sex. They were developed in clinical settings primarily to calculate drug dosages, not as fitness targets.
Men: 50 kg + 2.3 kg per inch over 5ft
Women: 45.5 kg + 2.3 kg per inch over 5ft
The most commonly used formula in clinical settings. Originally developed to calculate medication doses.
Men: 52 kg + 1.9 kg per inch over 5ft
Women: 49 kg + 1.7 kg per inch over 5ft
Slightly different coefficients. Often gives a lower result than Devine for taller people.
Men: 56.2 kg + 1.41 kg per inch over 5ft
Women: 53.1 kg + 1.36 kg per inch over 5ft
Higher baseline, lower increments — tends to give the highest result for shorter people.
Men: 48 kg + 2.7 kg per inch over 5ft
Women: 45.4 kg + 2.3 kg per inch over 5ft
The oldest formula. Gives a wide range. A popular rule of thumb in dietetics.
Get results from all four formulas plus your healthy BMI weight range, based on your height and sex.
Open Ideal Weight Calculator →For most purposes, the average of all four gives the most balanced estimate. If you're using it for a clinical purpose, check which formula your healthcare provider uses — Devine is the most common in medicine.
None of these formulas account for muscle mass, body composition or fitness level. A 170cm person who is very muscular will weigh more than these formulas suggest — and that's perfectly healthy. A thin person who is sedentary may hit the target weight but still have poor metabolic health.
Rather than a single target number, aim for a healthy weight range — typically defined as a BMI between 18.5 and 24.9. For a 170cm person this is approximately 53–72kg. Within that range, where your weight naturally settles when you eat well and exercise regularly is usually your healthy weight — individual to you, not a formula.