Ideal Weight Calculator

This calculator estimates your ideal weight range using several established formulas. The BMI method defines a healthy range as a BMI between 18.5 and 24.9, BMI being weight in kilograms divided by height in metres squared. The Devine formula (1974) and the Robinson formula (1983) each use height to produce a single ideal weight figure, and both were originally developed for drug-dosing calculations rather than for health goals. Miller (1983) and Hamwi (1964) do much the same job with different coefficients, and in practice the four land within about 5kg of one another.

The arithmetic is simple once you see it. Devine gives men 50kg plus 2.3kg for every inch of height over 5ft, and women 45.5kg plus 2.3kg per inch over 5ft. Miller starts higher and climbs more slowly, at 56.2kg plus 1.41kg per inch for men and 53.1kg plus 1.36kg per inch for women. Because each formula rests on height and sex alone, two people of identical height get an identical answer whatever their build, which is precisely where a single-figure target starts to creak.

Frame size is the usual correction. Run a tape measure round your dominant wrist: under 15cm counts as a small frame for a woman, 15 to 17cm as medium and over 17cm as large, while for men the cut-offs sit at 17cm and 19cm. Subtract 10% from the ideal body weight figure for a small frame and add 10% for a large one. Elbow breadth is more precise but harder to measure at home. Population differences matter too, with Asian populations typically assessed against lower thresholds and Pacific Islander populations higher ones.

Sample ranges built from Devine with that frame allowance applied in both directions start at 47 to 58kg for a height of 5ft 0in (152cm) and rise to 56 to 69kg at 5ft 4in (163cm). By 5ft 8in (173cm) the band sits at 64 to 79kg for women and 65 to 80kg for men, reaching 74 to 90kg and 75 to 92kg respectively at 6ft 0in (183cm), then 84 to 103kg and 86 to 105kg at 6ft 4in (193cm). NHS healthy weight ranges based on BMI differ slightly, so a height of 1.75m gives 56.7 to 76.6kg.

No single number is definitive, because body composition, frame size and ethnicity all influence what is healthy for you. The NHS uses BMI as a screening tool but acknowledges its limitations for muscular builds. A rugby player of 100kg at 1.85m records a BMI of 29.2, which reads as overweight, yet he might be carrying 12% body fat and be in elite condition. The opposite case, sometimes called skinny fat, sits inside the ideal weight band while carrying a high proportion of body fat. Body fat percentage, healthy at roughly 8 to 19% for men and 21 to 32% for women, describes that difference far better.

Enter your height and sex to see all three estimates. For a man of 178cm the healthy BMI range comes out at 58.6 to 78.9kg, with Devine suggesting 73.5kg and Robinson 72.6kg, giving a sensible target range of 68 to 79kg rather than one figure to hit. A waist under 94cm for men or 80cm for women, and a waist-to-height ratio under 0.5, tell you more about risk than the number on the scale.

Moving towards that range is best done at the NHS pace of 0.5 to 1kg a week, which comes from a deficit of 500 to 1,000 kcal a day below your total daily energy expenditure. Eating 1.6 to 2.2g of protein per kg of bodyweight and training with weights two or three times a week protects muscle while you lose fat. Very low intakes, under 1,200 kcal a day for women or 1,500 for men, tend to backfire through metabolic adaptation and muscle loss. Weigh yourself weekly in the morning, after the toilet and before food, expect a plateau after three or four months, and consider a two-week break at maintenance calories before carrying on. If you are concerned about your weight, your GP can take body composition, waist circumference and medical history into account.