Free ideal weight calculator
Find your ideal body weight in two seconds. Enter your sex and your height and the calculator returns your ideal weight using the Robinson formula (1983) — with the four classic formulas compared and an ideal-weight-by-height chart, updated live, as you type.
On this page14 sections
Ideal weight formulas are population averages. Athletes and muscular individuals may have a healthy weight above the calculated range.
Results are estimates. Consult a professional.
What is ideal body weight?
Ideal body weight (IBW) is an estimate of a healthy weight for your height and sex, produced by a simple formula. It is a single reference number — a starting point for the conversation about weight, not a medical verdict. This ideal weight calculator uses the Robinson formula (1983), one of the most widely cited IBW equations, and returns your ideal weight in kilograms the moment you enter your sex and height.
It helps to know where these formulas come from. IBW equations were originally built in the 1960s–80s to help clinicians estimate drug doses and ventilator settings — not to set personal weight goals. They take only two inputs: height and sex. They know nothing about your age, your build, how much muscle you carry, or your body-fat percentage. That is exactly why the result is best read as a rough guide rather than a target — a point this page returns to below.
The Robinson formula — how this calculator works
Every classic ideal-weight formula shares the same shape: a base weight for the first 5 feet (60 inches) of height, plus a fixed amount added for every inch above that. The Robinson formula — the one this calculator uses — sets the base and per-inch increment as follows.
Two things follow from this. First, ideal weight rises in a straight line with height — each inch over 5 feet adds 1.9 kg for men and 1.7 kg for women, with no curve. Second, at exactly 5 feet tall the formula returns the base weight itself: 52 kg for a man, 49 kg for a woman. Everything above that is the per-inch increment doing its work.
A worked example using the ideal weight calculator
Tom is a man who is 5 ft 10 in (177.8 cm) and wants to know his ideal weight. Here is exactly how the calculator works it out with the Robinson formula.
Step 1 — Convert the height to inches
The formula counts inches over 5 feet, so the height goes to inches first: 177.8 cm ÷ 2.54 = 70 inches. That is exactly 10 inches over the 60-inch (5 ft) base.
Step 2 — Apply the male Robinson formula
Start from the male base of 52 kg and add 1.9 kg for each of the 10 inches over 5 feet: 1.9 × 10 = 19 kg. So 52 + 19 = 71 kg.
Step 3 — Read the result
Now put that in context. A healthy BMI range (18.5–24.9) for someone 177.8 cm tall spans roughly 58.5 kg to 78.7 kg — and Tom's 71.0 kg ideal weight sits comfortably inside it, nearer the middle. That is the right way to read an IBW number: as one point inside a healthy band, not as a single line you must land on. The next sections show the full band and how the four classic formulas compare.
The four ideal weight formulas compared
Robinson is one of four classic IBW formulas you will see across calculators. They share the same base-plus-increment design but use slightly different numbers, so they give a small spread of answers rather than one figure. Here is how each is defined.
- Hamwi (1964) — the earliest, developed for nutrition assessment and still used by dietitians. Male: 48 kg + 2.7 kg/inch over 5 ft; female: 45.5 kg + 2.2 kg/inch.
- Devine (1974) — built for drug dosing and the most common in clinical medicine. Male: 50 kg + 2.3 kg/inch; female: 45.5 kg + 2.3 kg/inch.
- Robinson (1983) — a refinement of Devine using newer insurance data; the formula this calculator uses. Male: 52 kg + 1.9 kg/inch; female: 49 kg + 1.7 kg/inch.
- Miller (1983) — published the same year, with the highest base but the smallest per-inch increment. Male: 56.2 kg + 1.41 kg/inch; female: 53.1 kg + 1.36 kg/inch.
| Formula | Man, 5 ft 10 in | Woman, 5 ft 5 in |
|---|---|---|
| Hamwi (1964) | 75.0 kg (165 lb) | 56.5 kg (125 lb) |
| Devine (1974) | 73.0 kg (161 lb) | 57.0 kg (126 lb) |
| Robinson (1983) — this tool | 71.0 kg (157 lb) | 57.5 kg (127 lb) |
| Miller (1983) | 70.3 kg (155 lb) | 59.9 kg (132 lb) |
Each formula at two example heights. Robinson is the value this calculator returns.
Ideal weight vs. the healthy BMI range
An IBW formula gives you one number; the healthy BMI range gives you a band. The two answer slightly different questions, and the band is usually the more honest tool. A healthy weight is any weight that puts your BMI between 18.5 and 24.9 — and for any given height that is a range several kilograms wide, not a single point.
The useful way to combine them: treat the Robinson number as a reference point inside the healthy band. If your ideal weight lands near the middle of your BMI range — as it does for most heights — the two agree. Where they can diverge is at the extremes of build: a muscular person can sit above their IBW and above a BMI of 25 while carrying very little fat, because neither measure can tell muscle from fat. For the full band at your own height, use the healthy weight calculator, and to place yourself on the BMI scale use the BMI calculator.
Ideal weight by height chart
Most people want to see the whole range, not just their own number. The chart below runs the Robinson formula — the one this calculator uses — across common heights for both sexes. Find the height nearest yours and read across.
| Height | Ideal weight (men) | Ideal weight (women) |
|---|---|---|
| 5 ft 0 in (152 cm) | 52.0 kg (115 lb) | 49.0 kg (108 lb) |
| 5 ft 2 in (158 cm) | 55.8 kg (123 lb) | 52.4 kg (116 lb) |
| 5 ft 4 in (163 cm) | 59.6 kg (131 lb) | 55.8 kg (123 lb) |
| 5 ft 6 in (168 cm) | 63.4 kg (140 lb) | 59.2 kg (130 lb) |
| 5 ft 8 in (173 cm) | 67.2 kg (148 lb) | 62.6 kg (138 lb) |
| 5 ft 10 in (178 cm) | 71.0 kg (157 lb) | 66.0 kg (146 lb) |
| 6 ft 0 in (183 cm) | 74.8 kg (165 lb) | 69.4 kg (153 lb) |
| 6 ft 2 in (188 cm) | 78.6 kg (173 lb) | 72.8 kg (161 lb) |
| 6 ft 4 in (193 cm) | 82.4 kg (182 lb) | 76.2 kg (168 lb) |
Robinson formula (1983): men 52 + 1.9/inch, women 49 + 1.7/inch over 5 ft. Kilograms are the calculator's value at each exact height; pounds are rounded.
The pattern is a straight line: every two inches of height adds about 3.8 kg of ideal weight for men and 3.4 kg for women. Because it is linear, you can read between the rows — an inch is about half a row.
Body frame size and ideal weight
The classic formulas use only height and sex, which means a small-boned and a large-boned person of the same height get the same answer — even though the large-framed person naturally carries more weight in bone and structure. Frame size is the usual hand-adjustment for this. It is estimated from your wrist circumference relative to your height, and sorted into small, medium, or large.
- Small frame — subtract roughly 10% from the formula's ideal weight.
- Medium frame — use the formula's value as-is.
- Large frame — add roughly 10% to the formula's ideal weight.
Why ideal weight is a rough guide, not a target
It is worth being blunt about what an IBW number can and cannot tell you. These formulas were built decades ago to help with drug dosing and clinical estimates, not to set a personal goal weight. They factor in only height and sex — and as Calculator.net puts it, "there are no considerations for physical handicaps, people on the extreme ends of the spectrum, activity levels, or muscle mass to body fat ratios."
- It ignores body composition. Muscle weighs more than fat, so a fit, muscular person can be "over" their ideal weight while carrying very little fat. The formula can't tell the difference.
- It ignores age and build. One number is applied to a 25-year-old and a 70-year-old of the same height, and to slight and stocky builds alike.
- It is one formula's opinion. The four classic equations disagree by several kilograms at the same height, and none is provably "right."
- It is adults-only. All four formulas are for adults aged 18 and over; children and teens are assessed against age-and-sex BMI-for-age growth charts instead.
How to use this ideal weight calculator sensibly
Used as one reference among several, an ideal weight figure is genuinely useful. Here is a sensible way to read it.
- Get your number, then widen it to a band. Take the Robinson result and allow roughly 10% either side for frame and build — that band, not the single number, is your realistic healthy range.
- Cross-check against your healthy BMI range. If your ideal weight sits inside the 18.5–24.9 BMI band for your height, the two agree and you're in good shape.
- Check body composition if you're muscular. If you lift or carry obvious muscle, an IBW or BMI "over" reading may be misleading — body-fat percentage is the better tool.
- Track the trend, not the target. Where you're heading matters more than hitting an exact figure; pair this with a calorie or weight-loss plan to actually move it.
To go deeper, pair this tool with the healthy weight range, the BMI calculator, the body fat percentage calculator, and — if you're curious how your height itself ranks — the height percentile calculator.
Data sources and methodology
The calculator uses the Robinson formula (1983) — male 52 kg + 1.9 kg per inch over 5 feet, female 49 kg + 1.7 kg per inch — converting your height from centimetres to inches internally. The comparison table also shows the Hamwi (1964), Devine (1974), and Miller (1983) formulas. The healthy-weight band uses the WHO/CDC healthy BMI range of 18.5–24.9. Frame-size adjustments follow the standard wrist-circumference convention (±10% for small/large frames). All four IBW formulas apply to adults aged 18 and over.
Robinson JD, Lubowe II / Robinson, Lehman, Munro et al. — ideal body weight formula (1983); Devine BJ (1974); Hamwi GJ (1964); Miller DR et al. (1983).Ideal weight formulas, frame-size method, and adults-only limitation: Calculator.net — Ideal Weight Calculator.Healthy BMI range (18.5–24.9): World Health Organization / US NHLBI.Frequently asked questions about the free ideal weight calculator
About this ideal weight calculator
This ideal weight calculator runs entirely in your browser. Your height and sex never leave your device — nothing is sent to a server, logged, or shared. It applies the Robinson formula (1983), converting your height from centimetres to inches internally, and returns your ideal weight in kilograms, updating instantly on every change.
Calculators Cloud offers 400+ free tools with no sign-up. The whole Health calculators shelf includes the healthy weight range, BMI, Body fat %, and height percentile tools alongside this one. Or browse the full calculator directory.