What Is an Ideal Weight Calculator?

Type “ideal weight” into any search engine and you’ll find a dozen conflicting answers, because several respected formulas each produce a slightly different number for the same person. An ideal weight calculator estimates a reference body weight from your sex and height. The CalcFinity ideal weight calculator shows all four classic equations side by side — Robinson, Miller, Devine, and Hamwi — along with the healthy BMI weight range for your height, so you see the full picture instead of fixating on one figure. Enter your height in feet and inches or in centimeters, pick your sex, and every result updates instantly in both kilograms and pounds.

How It Works

All four formulas follow the same pattern: a base weight assigned at 5 feet tall, plus a fixed number of kilograms for each inch above that. They differ only in their base weights and per-inch increments, which is why their answers cluster within a few kilograms of one another rather than agreeing exactly.

Interestingly, none of these equations came from studies of health or appearance. Devine’s was published in 1974 for estimating drug doses; Hamwi’s appeared in a 1964 diabetes handbook; Robinson and Miller proposed refinements in 1983 against actuarial tables. They persist because they’re simple — not because any one is definitively “right.”

The Devine formula (the most widely used in medicine)

Robinson uses 52 kg + 1.9 kg/inch for men (49 + 1.7 for women), Miller uses 56.2 + 1.41 (53.1 + 1.36), and Hamwi uses 48 + 2.7 (45.5 + 2.2).

The healthy BMI range

The headline range shown by the calculator is computed separately from the formulas, using the healthy BMI band:

Worked Example: A 5’10” Man

Take a man who is 5’10” (10 inches over 5 feet). Robinson gives 52 + 1.9 × 10 = 71.0 kg (156.5 lb); Miller gives 56.2 + 1.41 × 10 = 70.3 kg (155.0 lb); Devine gives 50 + 2.3 × 10 = 73.0 kg (160.9 lb); and Hamwi gives 48 + 2.7 × 10 = 75.0 kg (165.3 lb).

His healthy BMI range spans 58.5 – 78.7 kg (128.9 – 173.5 lb) — notice that all four formula results sit comfortably inside it. A spread of 20 kilograms can all be “healthy” for the same height.

Think in Ranges, Not Targets

The most useful takeaway here is not any single number — it’s the width of the healthy range. Two people of identical height can carry very different amounts of muscle, bone, and fat and both be perfectly healthy; athletes routinely weigh more than every formula suggests while carrying less fat than average. Frame size, ethnicity, and body composition all shift where an individual naturally lands, and none of the classic equations account for them. Treat the results as a reference band, not a goal to chase, and pay more attention to strength, stamina, and the markers your doctor actually measures.

Common Mistakes to Avoid

The most common mistake is treating a single formula’s output as a personal target. If the Devine formula says 73.0 kg and you weigh 78, that is not a five-kilogram “problem” — it may not be a problem at all, since 78 kg still sits inside the healthy BMI range for a 5’10” man. These equations were calibrated for drug dosing and clinical shorthand, not for individual weight goals, and the four of them disagree with each other by several kilograms for exactly that reason. When the formulas themselves can’t agree on your “ideal,” chasing any one of them to the decimal point is chasing noise.

Height entry errors are the other frequent trap. In feet-and-inches mode, the inches field is the remainder after full feet — a 5’10” person enters 5 and 10, not 5 and 70, and not 70 in the feet field. Mixing up centimeters and inches produces even stranger results, which is why the calculator refuses heights outside 4’7”–7’6” (140–229 cm). Finally, remember the formulas assume adults at least 5 feet tall: applying them to children, teenagers who are still growing, or adults at the extremes of height stretches them well past the data they were built on.

Frequently Asked Questions