Ideal Weight Calculator
See what the classic ideal weight formulas and the healthy BMI range say for your height, plus how much protein to aim for each day.
Protein
How your ideal weight is worked out
Your numbers, step by step: the four classic formulas, then your protein.
- 1
Inches over 5 ft
70.1 in − 60 = 10.1 in
- 2
Base plus a bit
Devine: 50 + 2.3 × 10.1 = 73.2 kg
- 3
Average all four
71.1, 70.4, 73.2, 75.2 → 72.5 kg
- 4
Your daily protein
1.3 g × 80 kg = 104 g
Read more: the formulas, a worked example, frame size and protein ranges
What "ideal weight" means here
There is no single perfect weight. The formulas below were written by doctors in the 1960s to 1980s, mostly to work out medicine doses, and each gives one figure for your height and sex. The healthy BMI range is wider and is what most health services use today. Treat all of them as a rough guide: muscle, frame, age and where you carry fat all matter, and none of this is a diagnosis.
The formula
Ideal weight = base weight at 5 ft + a set amount for every inch over 5 ft
Healthy BMI range = 18.5 × height in metres² to 24.9 × height in metres²
Adjusted body weight = ideal + 0.4 × (your weight − ideal)
Protein a day (g) = grams per kg for your goal and activity × weight in kg
| Formula | Men | Women |
|---|---|---|
| Robinson (1983) | 52 kg + 1.9 kg per inch | 49 kg + 1.7 kg per inch |
| Miller (1983) | 56.2 kg + 1.41 kg per inch | 53.1 kg + 1.36 kg per inch |
| Devine (1974) | 50 kg + 2.3 kg per inch | 45.5 kg + 2.3 kg per inch |
| Hamwi (1964) | 48 kg + 2.7 kg per inch | 45.5 kg + 2.2 kg per inch |
| Broca, modified | (height in cm − 100) × 0.9 | (height in cm − 100) × 0.85 |
| Lorentz | cm − 100 − (cm − 150) ÷ 4 | cm − 100 − (cm − 150) ÷ 2 |
"Per inch" means each inch over 5 feet (152.4 cm). Below 5 feet the same line is carried on downwards, which the authors never tested, so treat results for shorter adults with extra care. Hamwi was first written in pounds (men 106 lb + 6 lb per inch, women 100 lb + 5 lb per inch); the kilogram version above is the one most calculators use.
Worked example
A man 178 cm tall weighing 80 kg. 178 ÷ 2.54 = 70.08 inches, which is 10.08 inches over 5 ft.
- Robinson: 52 + 1.9 × 10.08 = 71.1 kg
- Miller: 56.2 + 1.41 × 10.08 = 70.4 kg
- Devine: 50 + 2.3 × 10.08 = 73.2 kg
- Hamwi: 48 + 2.7 × 10.08 = 75.2 kg
- Average of the four: (71.15 + 70.41 + 73.18 + 75.21) ÷ 4 = 289.95 ÷ 4 = 72.5 kg, a BMI of 72.5 ÷ 1.78² = 22.9
- Broca: (178 − 100) × 0.9 = 70.2 kg. Lorentz: 178 − 100 − 28 ÷ 4 = 71.0 kg. So the six formulas span 70.2 to 75.2 kg.
- Healthy BMI range: 1.78² = 3.1684, so 18.5 × 3.1684 = 58.6 kg to 24.9 × 3.1684 = 78.9 kg. With the lower Asian cut-off the top is 22.9 × 3.1684 = 72.6 kg.
- At 80 kg he is 1.1 kg above the healthy BMI range (BMI 25.2) and at 80 ÷ 73.18 = 109% of his Devine ideal weight. His adjusted body weight is 73.18 + 0.4 × (80 − 73.18) = 75.9 kg.
- Protein, moderately active and keeping his weight: 1.2 to 1.4 g per kg, aiming for the middle, 1.3 g. 1.3 × 80 = 104 g a day (range 96–112 g), or about 104 ÷ 3 = 34.7 g at each of three meals. That's 104 × 4 = 416 kcal from protein.
Frame size
Divide your height by your wrist size (both in cm or both in inches, measured just above the wrist bone). This is the method from Grant (1980) used in many nutrition textbooks.
| Height ÷ wrist | Small frame | Medium frame | Large frame |
|---|---|---|---|
| Men | over 10.4 | 9.6 – 10.4 | under 9.6 |
| Women | over 11.0 | 10.1 – 11.0 | under 10.1 |
A small frame takes 10% off each formula and a large frame adds 10%, following Hamwi's own rule. We apply it to all six formulas; the BMI range doesn't change. Example: 178 ÷ 17.5 cm = 10.2, a medium frame.
Protein guide (grams per kg of body weight a day)
| Activity | Stay as I am | Lose fat, keep muscle | Build muscle |
|---|---|---|---|
| Sedentary | 0.8 – 1.0 | 1.0 – 1.2 | 1.2 – 1.6 |
| Light | 1.0 – 1.2 | 1.2 – 1.6 | 1.4 – 1.8 |
| Moderate | 1.2 – 1.4 | 1.4 – 1.8 | 1.6 – 2.0 |
| Very active | 1.4 – 1.7 | 1.6 – 2.2 | 1.6 – 2.2 |
| Athlete / strength most days | 1.6 – 2.0 | 1.8 – 2.4 | 1.8 – 2.2 |
Divide by 2.2 for grams per pound. The target shown is the middle of the range. Where these come from: 0.8 g/kg is the adult RDA, the minimum for most healthy, inactive adults (US Institute of Medicine). Joint guidance from the American College of Sports Medicine and sports dietitians suggests 1.2–2.0 g/kg for active people, and a 2018 review of 49 studies (Morton and others) found muscle gains from strength training level off around 1.6 g/kg, with 2.2 g/kg as a generous upper end. Eating more protein while eating less overall helps keep muscle. For people aged 65+ we use at least 1.0–1.2 g/kg (PROT-AGE group, 2013); in pregnancy at least 1.1 g/kg and when breastfeeding at least 1.3 g/kg (Institute of Medicine). Checked on 10 October 2026.
If your BMI is 30 or more, working protein out from your full weight can overshoot, so Auto uses your adjusted body weight instead. Spreading protein over the day helps; about 0.4–0.55 g per kg at a meal is roughly the most your muscles make use of at once (Schoenfeld and Aragon, 2018). Most health bodies suggest protein makes up about 10–35% of daily calories, at 4 kcal (17 kJ) per gram.
Its limits
- These formulas are for adults. For children and teenagers, use BMI-for-age growth charts.
- Muscular people can be heavier than every formula and still be healthy.
- If you have kidney disease or another condition, or you're unsure, ask your doctor or a dietitian before raising your protein.
General information, not medical advice. Talk to a doctor or dietitian about what your numbers mean for you.
Common questions
How is ideal weight calculated?
Most classic formulas start with a base weight at 5 feet and add a set amount for every inch over that. Devine, for example, is 50 kg plus 2.3 kg per inch for men and 45.5 kg plus 2.3 kg per inch for women. This calculator also shows the healthy BMI range: 18.5 to 24.9 × your height in metres squared.
Which ideal weight formula is most accurate?
None is perfect. Robinson, Miller, Devine and Hamwi were written by doctors in the 1960s to 1980s, mostly to work out medicine doses, and each gives one figure for your height and sex. The healthy BMI range is wider and is what most health services use today, so treat all of them as a rough guide.
What is the ideal weight for a man 178 cm tall?
For a man 178 cm tall (about 5 ft 10 in), the four classic formulas give 70.4 to 75.2 kg, an average of 72.5 kg. The healthy BMI range for that height is wider, 58.6 to 78.9 kg. Muscle, frame and age all matter, so use these as a guide rather than a target.
How does frame size change ideal weight?
Divide your height by your wrist size, both in the same unit. For men, over 10.4 is a small frame and under 9.6 is large; for women, over 11.0 is small and under 10.1 is large. A small frame takes 10% off each formula and a large frame adds 10%, while the BMI range stays the same.
How much protein do I need a day?
The adult minimum is 0.8 g per kg of body weight for most healthy, inactive adults. Active people often aim for 1.2–2.0 g per kg, and muscle gains from strength training level off around 1.6 g per kg. The calculator picks a target from your goal and activity; ask a doctor first if you have kidney disease.
Can I be healthy above my ideal weight?
Yes. Muscular people can be heavier than every formula and still be healthy, because the formulas only look at height and sex. Muscle, frame, age and where you carry fat all matter, so treat the results as a rough guide, not a diagnosis.
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