Ideal Weight Calculator
Calculate your ideal body weight using four evidence-based formulas.
Estimate a healthy target weight range using four established clinical formulas and BMI.
| Formula | Year | Ideal (kg) | Ideal (lbs) |
|---|
The Four Formulas Explained
Devine formula (1974)
Developed by Dr. B.J. Devine originally for calculating antibiotic and drug doses in patients where lean body tissue — not total weight — determines how a drug distributes and clears. Men: 50 kg + 2.3 kg per inch over 5 feet; Women: 45.5 kg + 2.3 kg per inch over 5 feet. It remains the most widely used ideal body weight formula in clinical medicine, particularly for medications like aminoglycosides, digoxin, and certain chemotherapy regimens.
Robinson formula (1983)
A refinement of Devine with slightly lower per-inch increments: Men: 52 kg + 1.9 kg per inch over 5 feet; Women: 49 kg + 1.7 kg per inch over 5 feet. The lower multipliers produce estimates a little below Devine for taller individuals. It is not significantly more accurate than Devine but provides a useful comparison — if the two agree closely, confidence in the estimate is higher.
Miller formula (1983)
Published in the same year as Robinson and takes a different approach to the base weight and increment: Men: 56.2 kg + 1.41 kg per inch over 5 feet; Women: 53.1 kg + 1.36 kg per inch over 5 feet. The higher base weight and lower increment mean Miller gives lower estimates than Devine for shorter individuals and higher estimates for taller individuals. It is the least used of the four in clinical practice.
Hamwi formula (1964)
The oldest of the four, developed by G.J. Hamwi in 1964 for estimating energy needs in patients with diabetes. Men: 48 kg + 2.7 kg per inch over 5 feet; Women: 45.5 kg + 2.2 kg per inch over 5 feet. The higher per-inch increment means Hamwi tends to give the highest estimates for taller people. Like the other formulas, it was created for a clinical purpose — not as a fitness or aesthetic target.
Healthy BMI range
The World Health Organisation defines a healthy BMI as 18.5–24.9 kg/m². Converting this to a weight range at your specific height gives a band rather than a single number — at 175 cm, that is approximately 56.7–76.2 kg. Unlike the clinical formulas above, the BMI range was derived from population mortality data and represents a health risk boundary rather than a dosing estimate. See the body fat calculator for a body-composition-based assessment that goes beyond scale weight alone.
Worked example
Male, 178 cm (5 ft 10 in — 10 inches over 5 feet): Devine = 50 + (2.3 × 10) = 73.0 kg; Robinson = 52 + (1.9 × 10) = 71.0 kg; Miller = 56.2 + (1.41 × 10) = 70.3 kg; Hamwi = 48 + (2.7 × 10) = 75.0 kg. Average across all four: 72.3 kg. BMI healthy range at 178 cm: 58.6–78.9 kg. All four formula values fall comfortably within the healthy BMI band, confirming broad agreement at this height.
Related calculations
For a range rather than a single figure, the healthy weight calculator gives the span your height supports, and the BMI calculator shows where a given weight sits within it. Body composition matters too — the body fat calculator estimates what that weight is made of.
Ideal Weight vs Healthy Weight vs Goal Weight
The clinical origin of "ideal weight"
The Devine, Robinson, Miller, and Hamwi formulas were derived for pharmacokinetic calculations — estimating how drugs distribute in the body based on lean tissue volume. None was intended to define a fitness target or aesthetic ideal. The word "ideal" in this context means the weight at which a drug dose would behave predictably, not the weight at which you would look or feel best.
What "healthy weight" actually means
"Healthy weight" (BMI 18.5–24.9) is a population-level classification derived from studies linking BMI to mortality and disease risk. Any weight within the band carries broadly comparable health risk — a person at BMI 19 is not meaningfully healthier than one at BMI 24. The clinical formula values and the BMI range often overlap but can differ. Where they do, the BMI range is generally the more appropriate reference for health planning. See the healthy weight calculator for your specific range.
Goal weight is personal
A realistic goal weight should account for how you feel and function, your energy levels, sustainable eating and exercise habits, blood markers (blood pressure, blood glucose, cholesterol), and body composition — not just what a formula outputs. The four-formula spread (typically 5–8 kg) reflects genuine uncertainty: the formulas collectively suggest a range, not a single point. If your weight sits within that spread and you have healthy blood markers, aiming lower has no clinical basis. The macro calculator sets calorie and protein targets for whatever weight goal you personally choose.
When the formulas don't apply
All four formulas use height as the only input — they cannot account for muscle mass. A competitive athlete or regular strength trainer may carry 10–15 kg more muscle than an average person of the same height, placing them well above the formula values while having excellent body composition and health markers. In this case the formula outputs are not meaningful targets. A body fat percentage measurement — via DEXA scan or the Navy circumference method — gives a far more relevant picture of health for muscular individuals.
Practical Next Steps
If your weight is within the healthy range
If your current weight falls within the BMI 18.5–24.9 band — and particularly if it overlaps with the formula spread — maintaining is a valid clinical goal. Focus on body composition, energy levels, and blood markers rather than trying to reach a specific formula number. A small reduction in body fat while preserving lean mass (body recomposition) often delivers more health benefit than a further drop in scale weight. Track lean mass alongside weight using the lean body mass calculator.
If your weight is above the healthy range
A practical first target is the top of the healthy BMI band for your height (BMI 24.9) — this is a meaningful health improvement even if you don't reach the formula average. A loss rate of 0.5–1% of body weight per week preserves muscle better than faster loss. Use the macro calculator to find your TDEE and set a daily calorie deficit. A 5–10% reduction in body weight improves blood pressure, blood glucose, and cholesterol risk substantially, even before reaching the healthy range.
If your weight is below the healthy range
If your weight sits below BMI 18.5, the clinical formula average gives an indicative target, but the priority is restoring adequate energy intake and lean mass. A modest surplus of 250–500 kcal above TDEE combined with adequate protein (1.6 g per kg of body weight) supports gradual, healthy weight gain. If low body weight is unintentional or persistent, consult a GP — it may reflect an underlying condition. The macro calculator set to a weight gain goal provides personalised calorie and protein targets.
Check blood markers alongside scale weight
Scale weight and formula outputs are single-number summaries of a complex picture. Also check: waist circumference (elevated risk above 88 cm for women, 102 cm for men); blood pressure (target below 120/80 mmHg); fasting blood glucose (target below 5.6 mmol/L); and total and LDL cholesterol. In the UK, adults aged 40–74 are eligible for a free NHS Health Check that covers all of these. Weight near a formula target with any blood marker out of range is a more pressing health concern than the exact formula result.
Frequently Asked Questions
How is ideal body weight calculated?
This calculator uses four formulas: Devine (1974), Robinson (1983), Miller (1983), and Hamwi (1964). The Devine formula — the most widely used clinically — is: men: 50 kg + 2.3 kg per inch over 5 feet; women: 45.5 kg + 2.3 kg per inch over 5 feet. The average across all four is shown alongside the BMI 18.5–24.9 healthy weight range for your height. Results typically vary by 5–8 kg across the four formulas.
Which ideal weight formula is most accurate?
No single formula is universally accurate — all four were derived for clinical drug dosing, not fitness targets. Devine is the most validated and widely cited in pharmacokinetics. The spread of values across all four is itself useful: close agreement suggests higher confidence. For most people, the BMI healthy range (18.5–24.9) is a better-evidenced health target than any single formula value.
What is the difference between ideal weight and healthy weight?
"Ideal weight" (Devine, Robinson, Miller, Hamwi) was derived for drug dosing calculations and estimates the weight at which medications distribute predictably through lean tissue. Healthy weight (BMI 18.5–24.9) is a population health risk classification based on mortality data. The two often overlap but sometimes differ. Neither accounts for body composition — a muscular person may be above all formula values while having excellent health markers.
Should I aim for my ideal weight formula result?
These formulas provide a reference range, not a personal health prescription. Health is more accurately assessed through blood pressure, fasting blood glucose, cholesterol, and waist circumference alongside weight. If your weight is within the BMI healthy range and blood markers are normal, aiming lower at a formula target is not clinically indicated. For a personalised calorie and protein plan to reach any weight goal, use the macro calculator.
Evidence & Methodology
How This Page Is Grounded
Method
Compares the Devine, Robinson, Miller and Hamwi equations with a BMI-based weight range.
Important limitation: The historical equations were developed for clinical estimation and do not define a universally ideal personal weight.
Primary Sources
- Universal equation for estimating ideal body weight PubMed
- Obesity and overweight World Health Organization
Quality Checks
Each formula is calculated independently and checked at the 5-foot baseline and multiple heights.
See how sources are selected and corrections are handled in our Editorial & Calculation Methodology, and which automated checks this page has to pass in How We Test.