Estimate your healthy weight range using four established medical formulas
Ideal weight formulas provide estimates based on population data and do not account for muscle mass, body composition, or individual health factors. Consult your GP or a registered dietitian for personalised weight guidance.
Ideal weight calculators estimate a healthy body weight based on your height, sex, and body frame size. Unlike BMI, which gives a single number that must be interpreted against a category table, ideal weight formulas provide a direct weight target in kilograms. This calculator uses four of the most widely referenced formulas in medical literature -- Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964) -- and presents an average alongside the individual results so you can see the range of estimates. Each formula was developed using different study populations and methodologies, which is why they produce slightly different results. The Devine formula is the most widely used in clinical practice, particularly for drug dosing calculations. Robinson and Miller were developed as refinements to Devine, and Hamwi is one of the earliest and simplest formulas. By showing all four, this calculator gives you a more complete picture than relying on any single estimate. It is important to understand that no ideal weight formula accounts for muscle mass, body fat distribution, or individual health markers. A rugby player and a sedentary office worker of the same height and sex will get the same result, despite having very different body compositions. For this reason, ideal weight should be treated as a rough guide rather than a precise target. The NHS recommends using BMI alongside waist circumference measurement for a more practical assessment of weight-related health risk. This calculator includes the BMI-based healthy weight range for comparison.
To estimate your ideal weight: 1. Enter your height in centimetres. If you know your height in feet and inches, convert to centimetres: multiply feet by 30.48 and inches by 2.54, then add together. For example, 5 foot 7 inches = (5 x 30.48) + (7 x 2.54) = 152.4 + 17.8 = 170.2 cm. 2. Select your sex. The formulas produce different results for males and females because the original studies found different height-to-weight relationships between sexes. 3. Select your frame size. If unsure, choose medium. To estimate your frame size, wrap your thumb and middle finger around your wrist: if they overlap, you have a small frame; if they just touch, medium; if they do not meet, large. Small frame reduces all estimates by 10%, large frame increases by 10%. 4. Review your results. You will see the average ideal weight across all four formulas, the range from lowest to highest formula, each individual formula result, and the BMI-based healthy weight range (18.5-24.9) for your height. The bar chart compares all these values visually.
All four formulas use height in inches, measured from 5 feet (60 inches) as a baseline: **Devine (1974):** Male: 50.0 + 2.3 x (height in inches - 60) Female: 45.5 + 2.3 x (height in inches - 60) **Robinson (1983):** Male: 52.0 + 1.9 x (height in inches - 60) Female: 49.0 + 1.7 x (height in inches - 60) **Miller (1983):** Male: 56.2 + 1.41 x (height in inches - 60) Female: 53.1 + 1.36 x (height in inches - 60) **Hamwi (1964):** Male: 48.0 + 2.7 x (height in inches - 60) Female: 45.4 + 2.2 x (height in inches - 60) For a 180cm male (70.87 inches), over-60 = 10.87 inches: - Devine: 50 + 2.3 x 10.87 = 75.0 kg - Robinson: 52 + 1.9 x 10.87 = 72.7 kg - Miller: 56.2 + 1.41 x 10.87 = 71.5 kg - Hamwi: 48 + 2.7 x 10.87 = 77.3 kg - Average: 74.1 kg Frame size adjustment applies a multiplier: small frame = 0.9x (10% less), medium = 1.0x, large = 1.1x (10% more). The BMI healthy range uses: weight = BMI x (height in metres)^2, where BMI boundaries are 18.5 (low) and 24.9 (high).
These formulas were developed decades ago using primarily Western populations and may not be equally applicable to all ethnic groups. The WHO and NHS note that health risks associated with body weight can differ by ethnicity -- for example, people of South Asian descent may face increased health risks at lower weights than these formulas suggest. If you have concerns about your weight, speak to your GP who can assess your individual circumstances including body composition, family history, and other health markers.