Ideal Weight Calculator

When to use it

Three classic formulas, one height, three different answers: that disagreement is the point of this page. Devine, Robinson and Miller were derived from different populations for different purposes, and none of them is a prescription. What they do provide is a cluster, and the healthy BMI band gives the range around it.

Use it to sanity-check a target you have been given, to understand why two charts disagree, or to see how wide the healthy range actually is at your height. It is not for children, and it says nothing about body composition.

How the maths works

Height is converted to inches. Devine: 50 + 2.3 × (inches − 60) for men, 45.5 + 2.3 × (inches − 60) for women. Robinson: 52 + 1.9 × (inches − 60) for men, 49 + 1.7 × for women. Miller: 56.2 + 1.41 × (inches − 60) for men, 53.1 + 1.36 × for women. All three are linear in height above five feet.

The band is separate: weight at BMI 18.5 to 24.9, which is 18.5 × height² to 24.9 × height² with height in metres. It is wider than any single formula because it is a range, not a point.

A worked example

A man 180 cm tall.

1. In inches: 180 ÷ 2.54 = 70.87, so 10.87 above five feet.
2. Devine: 50 + 2.3 × 10.87 = 75.0 kg.
3. Robinson: 52 + 1.9 × 10.87 = 72.6 kg; Miller: 56.2 + 1.41 × 10.87 = 71.5 kg.
4. Band: 18.5 × 1.8² = 59.9 kg to 24.9 × 1.8² = 80.7 kg.

The three formulas span 3.5 kg, while the band spans more than 20. That ratio is the most honest thing the page shows.

Heights compared

At 165 cm the female formulas give 56.9 kg (Devine), 57.4 kg (Robinson) and 59.8 kg (Miller), with a band of 50.4 to 67.8 kg.

Common mistakes

• Treating one number as the target. The formulas disagree by design; the band is the more useful message.
• Using it for children. Under 18, growth charts by age and sex are the correct reference.
• Ignoring frame and muscle. A broad frame or a trained physique sits legitimately above these figures.
• Losing the height. Comparing a weight from one height with a band from another is the most common arithmetic slip.

Keep exploring

• BMI Calculator — the screening figure behind the band.
• Body Fat Estimate (US Navy Method) — an estimate that adds waist and neck.
• BMI Calculator (Imperial) — the same band in pounds and inches.
• Guide: BMI, Calories and Water Intake.