Formula

Ideal Weight

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Published by MetaSys Limited · Page updated 19 September 2026 · Editorial policy. Educational information; not a medical review.

What Is Ideal Weight, and How Are the Formulas Different?

The concept of an "ideal body weight" has been debated in medicine for decades. Unlike BMI, which is a ratio applied to everyone equally, ideal weight formulas were developed for specific clinical purposes — mainly to calculate drug dosages in hospitals and to estimate a weight associated with good metabolic health for a given height. There is no single universally accepted formula, which is why we show you four.

The Four Formulas Explained

The Hamwi Formula (1964) was originally created for clinical nutrition and drug dosing. It starts from a base weight at 5 feet and adds a fixed amount per inch above that. For men: 106 lbs at 5'0" plus 6 lbs per inch above. For women: 100 lbs at 5'0" plus 5 lbs per inch above. It tends to give slightly higher estimates than the other formulas.

The Devine Formula (1974) is perhaps the most widely used in pharmacology, particularly for calculating medication doses in clinical settings. It was originally published to predict ideal weight for dosing gentamicin, an antibiotic. For men: 50 kg at 5'0" plus 2.3 kg per inch. For women: 45.5 kg at 5'0" plus 2.3 kg per inch. Its primary limitation is that it wasn't derived from population health data — it was a clinical convenience formula.

The Robinson Formula (1983) was developed as a revision to Devine, using actuarial data to better reflect weights associated with longevity. For men: 52 kg plus 1.9 kg per inch above 5 feet. For women: 49 kg plus 1.7 kg per inch above 5 feet. It generally produces slightly lower estimates than Devine for men.

The Miller Formula (1983), published the same year as Robinson, used a different dataset and tends to give the lowest estimates of the four, particularly for women. For men: 56.2 kg plus 1.41 kg per inch above 5 feet. For women: 53.1 kg plus 1.36 kg per inch above 5 feet.

Why the Results Differ Across Formulas

The variation between formulas — often 5–15 lbs at typical heights — reflects the fact that they were derived for different purposes using different datasets at different points in history. None of them accounts for muscle mass, body frame size, or body fat distribution. A 5'10" woman with substantial muscle development may be 20+ lbs above the Devine formula suggestion while being in excellent health. Conversely, someone at the "ideal" number could still have poor metabolic health if they carry little muscle and high visceral fat.

Setting a Realistic Weight Goal

Rather than targeting a specific ideal weight from a formula, consider a weight at which you feel energetic, perform well in the gym, maintain without excessive restriction, and have healthy metabolic markers (blood pressure, blood glucose, cholesterol). For most people, that falls somewhere within the range our calculator shows. Pick a number from that range that feels realistic for your body and lifestyle, then use our calorie deficit calculator to build a plan to get there.

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Ideal Weight — Frequently Asked Questions

Which ideal weight formula is most accurate?

None of the four formulas is definitively "most accurate" in a universal sense — they were each developed for different clinical purposes using different methods. Most current research suggests that the Devine formula remains the most widely used in clinical practice, particularly for drug dosing. For personal health goals, the average of all four formulas (shown as the average in our results) is a more balanced estimate than any single formula. More importantly, BMI and metabolic health markers are better indicators of health than ideal weight formula outputs.

Does ideal weight change with age?

The four formulas in our calculator are based solely on height and gender — they don't adjust for age. In practice, research suggests that the weight associated with lowest mortality risk increases slightly with age, particularly after 65. Older adults may benefit from being slightly above the formulas' suggestions to provide a reserve against illness and frailty. Muscle mass becomes especially important: two people of the same weight in their 60s can have very different health outcomes depending on their muscle-to-fat ratio.

What if I'm significantly above my ideal weight?

Focus on direction rather than destination. Research consistently shows that losing just 5–10% of your current body weight produces meaningful, measurable improvements in blood pressure, blood sugar, cholesterol, and joint stress — even if you remain above your "ideal" weight. Set an intermediate goal (e.g., lose 10–15 lbs in the next 3 months) rather than trying to reach the formula target all at once. Progressive, sustainable progress beats an ambitious goal abandoned after 6 weeks every time.

Do ideal weight formulas apply to athletes?

No — ideal weight formulas do not account for muscle mass and are essentially meaningless for athletes. A competitive powerlifter, rugby player, or bodybuilder will almost certainly be well above the formula outputs while being in excellent health. For athletes, body composition metrics (body fat percentage, lean mass) are far more useful than weight on a scale or ideal weight formula outputs. If you're athletic and training seriously, ignore these numbers as goal weights — they simply weren't designed for your body type.

How do I calculate how long it will take to reach my ideal weight?

Use our Calorie Deficit Calculator — enter your current weight, your ideal weight goal, and your desired timeframe. It will calculate your required daily calorie deficit and flag whether your timeline is safe or too aggressive. A realistic pace is 0.5–1 lb per week for most people, which means a 50-lb loss takes roughly 12–18 months. The timeline seems long, but those are the results that last — crash approaches almost always result in weight regain.

Ideal Weight Calculator

What Is Ideal Weight, and How Are the Formulas Different?

The Four Formulas Explained

Why the Results Differ Across Formulas

Setting a Realistic Weight Goal

Ideal Weight — Frequently Asked Questions

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