Ideal Body Weight
Calculator
Find your healthy weight range using four scientifically validated formulas — Devine, Robinson, Miller, and Hamwi — with frame size adjustment and personalised insights.
—
Ideal Body Weight Calculator: Find Your Healthy Weight Range
The concept of “ideal body weight” has evolved significantly over the past century — from insurance industry actuarial tables in the early 1900s to today’s evidence-based clinical formulas used in medicine and pharmacology. This free ideal body weight calculator uses four validated clinical formulas (Devine, Robinson, Miller, and Hamwi) to provide a range of estimates, giving you a more nuanced picture than any single formula can offer. Crucially, it presents these results in their appropriate context: as reference points for health conversations, not rigid targets to be pursued at any cost.
Quick reference: For a 5’7″ (170cm) male with medium frame, ideal weight estimates range from approximately 65.2–66.7 kg (144–147 lbs) across the four formulas, with an average of about 65.9 kg. Enter your details above for your personalised range.
What Is Ideal Body Weight?
Ideal body weight (IBW) is a theoretical target weight associated with optimal health outcomes for a given height and sex. The concept was originally developed in the 1960s–1980s by physicians who needed a practical way to calculate appropriate drug dosages for patients — many medications need to be dosed based on body weight, and using actual body weight in obese patients often leads to overdosing. The IBW formulas provided a standardised reference weight for this purpose.
Over time, IBW calculations became widely used in nutritional science, fitness, and general health contexts — though their original clinical purpose (drug dosing) remains an important application. It’s important to understand that these formulas were never intended as definitive health targets for individual people, and they carry significant limitations when applied outside their original clinical context.
The Four Ideal Body Weight Formulas
| Formula | Year | Male base (60″) | Male increment per inch | Female base (60″) | Female increment |
|---|---|---|---|---|---|
| Devine | 1974 | 50.0 kg | +2.3 kg/in | 45.5 kg | +2.3 kg/in |
| Robinson | 1983 | 52.0 kg | +1.9 kg/in | 49.0 kg | +1.7 kg/in |
| Miller | 1983 | 56.2 kg | +1.41 kg/in | 53.1 kg | +1.36 kg/in |
| Hamwi | 1964 | 48.0 kg | +2.7 kg/in | 45.4 kg | +2.2 kg/in |
All formulas use 60 inches (152.4 cm) as the base height, adding an increment for each additional inch of height. The Hamwi formula (1964) is the oldest and was developed specifically for diabetes patient care. The Devine formula (1974) is the most widely referenced in medical literature. Robinson and Miller (both 1983) were developed to refine the earlier formulas using larger population datasets. The calculator above displays all four results and their average, giving you a range rather than a single potentially misleading number.
How the Ideal Body Weight Calculator Formula Works
This calculator measures a reference weight for your height and sex, using four formulas that share the same basic structure: a base weight at 60 inches (152.4 cm), plus a fixed amount added for every inch above that. The units are always kilograms (with pounds shown in imperial mode). Read the average across all four formulas as a general reference point, and the spread between the lowest and highest formula as a sense of how much these established methods disagree with each other for your exact height. If you’ve selected a small or large frame, the calculator adjusts every formula’s result by ±10% before averaging. The formulas assume an average body composition; they don’t measure your actual muscle mass, bone density, or fat percentage, so someone with an athletic build will reasonably exceed these numbers while remaining in excellent health.
Identify the inputs
You enter height, biological sex, and optionally a frame size (small, medium, or large) and age, which affect the interpretation shown in the insight text.
Apply the formula
Each formula takes the number of inches your height exceeds 60, multiplies that by the formula’s per-inch increment, and adds the formula’s base weight. If a frame size is selected, the result is then multiplied by 0.9 (small) or 1.1 (large).
Perform the calculation
Using the calculator’s default example: a male at 170 cm (about 66.9 inches) with a medium frame. Devine: 50 + 2.3 × (66.9 − 60) = 50 + 15.9 = 65.9 kg. The other three formulas run the same way with their own base and increment, then all four are averaged.
Interpret the result
The averaged result, 65.9 kg for this example, is the calculator’s headline number. The formula range of 65.2 to 66.7 kg (the lowest to highest of the four individual results) shows how closely these four clinical estimates actually agree at this particular height.
3 Real-Life Examples
1. A petite woman using the small frame adjustment
A woman who is 5’2″ (157.5 cm) with a small frame wants her ideal weight range, using the small frame adjustment.
The formula range after adjustment runs from 44.8 to 50.2 kg. The small frame adjustment lowers every formula’s result by a tenth, reflecting a lighter skeletal structure relative to height.
2. A tall man using the large frame adjustment
A man who is 6’2″ (188 cm) with a large frame wants his estimate, using the large frame adjustment.
The formula range after adjustment runs from 83.6 to 94.4 kg, a wider spread than the small-frame example, since the per-inch increments diverge more at greater heights above the 60 inch baseline.
3. A woman with a medium frame at an average height
A woman who is 165 cm with a medium frame (no adjustment applied) wants a straightforward reference range.
Without a frame adjustment, this example shows how closely the four formulas actually agree for someone of average height, with all four results falling within about 3.5 kg of each other.
Ideal Weight vs BMI: Key Differences
Body Mass Index (BMI) and ideal body weight formulas both attempt to define healthy weight ranges based on height, but they approach the problem differently and have different strengths and weaknesses:
- BMI expresses weight relative to height squared (weight ÷ height²) and produces a single number categorised into underweight/normal/overweight/obese ranges (18.5–24.9 is the “normal” range). BMI is widely used in population health research because it correlates reasonably well with health risks at the population level.
- IBW formulas produce a target weight in kg/lbs rather than a ratio, making them more directly practical for clinical applications like drug dosing, nutritional assessment, and setting realistic weight goals in conversation with patients.
- Key limitation of both: Neither BMI nor IBW formulas account for body composition — the ratio of muscle, fat, bone, and water in the body. A muscular athlete may have an “overweight” BMI and exceed IBW estimates while having excellent metabolic health and low body fat. Conversely, a “normal” BMI person with low muscle mass and high fat percentage (called “skinny fat” or TOFI — Thin Outside, Fat Inside) may face metabolic risks invisible to BMI and IBW.
Factors That Affect Healthy Weight
Individual healthy weight is influenced by many factors that simple height-based formulas cannot capture:
- Muscle mass: Muscle is denser than fat — athletes, bodybuilders, and consistently active people carry significantly more lean mass, which rightfully pushes their optimal weight above IBW estimates
- Bone density: Skeletal mass varies significantly between individuals and ethnic groups — higher bone density supports higher body weight without health penalty
- Age: Optimal weight shifts across the lifespan. Children and adolescents use growth charts rather than adult formulas. Adults over 60 often maintain better health at weights slightly above traditional IBW estimates, which may help protect against bone loss and frailty
- Ethnicity: Population studies have found that health risk thresholds for BMI (and by extension IBW) differ by ethnicity. Asian populations show elevated metabolic risk at lower BMIs than the standard thresholds suggest
- Sex hormones: Testosterone and estrogen affect fat distribution patterns and healthy ranges beyond what sex alone captures
How to Achieve a Healthy Weight
Focus on food quality, not just calories
Sustainable weight management prioritises whole foods, adequate protein (1.6–2.2g/kg for active individuals), fibre, and micronutrient density over rigid calorie counting. Diet quality affects metabolism, satiety, and body composition beyond what total calories alone explain.
Build and preserve muscle mass
Resistance training 2–4× per week preserves or builds muscle mass during weight management, improving body composition without necessarily changing body weight. A person who loses 5kg of fat while gaining 3kg of muscle has dramatically improved health even though the scale shows only a 2kg change.
Prioritise sleep and stress management
Chronic sleep deprivation and high cortisol from stress directly impair metabolism, increase appetite (particularly for energy-dense foods), and promote fat storage — especially visceral (abdominal) fat. No diet or exercise programme fully compensates for consistently poor sleep.
Track body composition, not just weight
Body weight fluctuates by 1–3kg daily from water, food, and glycogen changes. More meaningful metrics include waist circumference, waist-to-hip ratio, body fat percentage (if measurable), energy levels, strength, and fitness markers rather than scale weight alone.
Important Notes
What this calculator does and doesn’t cover
This tool applies four established height-based formulas to the numbers you enter. A few things worth understanding before relying on the results:
- These formulas were developed decades ago for clinical drug dosing, not as personal fitness targets. Their accuracy for that original purpose doesn’t necessarily translate to being an ideal target weight for general health.
- Frame size is a rough self-assessment, not a measured value. The wrist-overlap test this calculator’s FAQ describes is a practical shortcut, not a precise skeletal measurement, so treat the ±10% adjustment as approximate.
- Age doesn’t change the underlying calculation. The formulas produce the same result regardless of the age you enter; only the insight text below the result adjusts its interpretation for people under 20 or over 60.
- None of the four formulas account for muscle mass, bone density, or body fat percentage. Athletic or heavily muscled individuals will reasonably and healthily exceed these estimates. See the CDC’s FAQ on BMI for a similar caveat that applies to body-composition-blind measurements generally.
- Rounding. Figures are rounded to one decimal place for display.
- Not medical advice. For personalized weight guidance, especially around drug dosing, pregnancy, or an existing health condition, consult a healthcare professional. The NIH’s weight management resources offer further reading on healthy weight in broader clinical context.
Related Health Calculators
Frequently Asked Questions
Calculate your ideal body weight range
Four validated formulas, personalised insights, and health education — free, instant, no sign-up required.
Calculate my ideal weight ↑