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Ideal Weight: What the Formulas Do — and Don't — Tell You

Health · 6 min read · Last updated September 2026

Quick answer: "Ideal weight" is not one number. The classic Devine formula gives a single kilogram figure from height alone, while the healthy-BMI method gives a range. For someone 1.75 m tall, Devine (male) says about 70.7 kg while the BMI range is 56.7–76.3 kg — both can be true, because they answer different questions.

The Devine formula (the classic single number)

Men: 50 kg + 2.3 kg per inch over 5 ft
Women: 45.5 kg + 2.3 kg per inch over 5 ft

Built in 1974 to dose medication, not to set fitness goals. Example: a 5′10″ (70-inch) man: 50 + 2.3 × 10 = 73.0 kg; a 5′10″ woman: 45.5 + 23 = 68.5 kg. It ignores muscle, age and frame entirely — that is a feature for drug dosing and a limitation for everything else.

The healthy-BMI range (a range, honestly)

Healthy weight range = 18.5 × height² to 24.9 × height² (kg)

At 1.75 m: 18.5 × 3.0625 = 56.7 kg up to 24.9 × 3.0625 = 76.3 kg — a 20-kilogram-wide band. The BMI range is broader than Devine precisely because bodies vary more than a dosing formula can express.

Why the two disagree — and which to use

Method5′10″ maleAnswers the question
Devine73.0 kg"What does a population-average body of this height weigh?"
Healthy BMI56.7–76.3 kg"What range is statistically associated with lower health risk?"

Use the range for context, not a target to hit exactly. A muscular 78 kg person at 1.75 m sits above the BMI band but is not unhealthy; a sedentary 70 kg person inside it may carry more risk than the number suggests. Pair the result with the BMI Calculator and — more informatively — a waist measurement or body-fat estimate.

Limitations: no height-only formula can see muscle mass, bone frame, age or fat distribution. Treat any "ideal weight" output as a conversation starter with real data, not a verdict.

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Frequently asked questions

What is the ideal weight for my height?

There is no single number. The healthy-BMI range for your height (18.5–24.9 × height in meters squared) is the most defensible reference band — for 1.75 m that is about 56.7–76.3 kg — and formulas like Devine give a narrower population average inside or near it.

How do I calculate ideal weight by hand?

Devine: men, 50 kg + 2.3 kg per inch over 5 feet; women, 45.5 kg + 2.3 kg per inch over 5 feet. For the BMI range, multiply your height in meters by itself, then by 18.5 and by 24.9.

Is ideal weight the same as healthy weight?

Not exactly. Ideal-weight formulas give one point estimate from height alone; healthy weight is better expressed as the BMI-associated range, which is wider because muscle, frame and body composition vary.

Why does the calculator show a range instead of one number?

Because a range is the honest output. Bodies at the same height legitimately differ by 15–20 kg while remaining healthy; a single kilogram figure implies precision the underlying data does not support.