Ideal weight calculator

The four classic ideal weight formulas for your height, next to the NHS healthy range. They give different answers, which is why a range is more useful than one number.

Your details

Healthy range for 5 ft 8 in

8 st 10 lb to 11 st 10 lb

The NHS BMI range

Devine (1974)10 st 1 lb (BMI 21.4)
Robinson (1983)9 st 12 lb (BMI 21.0)
Miller (1983)10 st 1 lb (BMI 21.4)
Hamwi (1964)9 st 13 lb (BMI 21.2)
The four formulas averaged10 st 0 lb
How far they disagree3 lb
BMI range used18.5 to 24.9

The formulas each give one number, and they rarely agree. They were made to work out medicine doses, not goals, so the BMI range is the better guide.

Formulas compared

Why the four answers disagree

Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964) were all fitted to small groups, mostly to work out medicine doses. Each row shows the BMI that formula implies for your height, plus the average of all four and the gap between the highest and lowest. A gap of a stone or more is normal, which is why the NHS BMI range is the better guide.

The working

Where the formulas come from

Each formula starts with a base weight at 5 ft and adds a set amount for every inch above that. Devine, the most famous, gives women 45.5 kg plus 2.3 kg an inch and men 50 kg plus 2.3 kg an inch.

Formula	Women	Men
Devine (1974)	45.5 + 2.3 per inch	50 + 2.3 per inch
Robinson (1983)	49 + 1.7 per inch	52 + 1.9 per inch
Miller (1983)	53.1 + 1.36 per inch	56.2 + 1.41 per inch
Hamwi (1964)	45.5 + 2.2 per inch	48 + 2.7 per inch

For a woman of 5 ft 8 in, Devine gives 45.5 + (8 × 2.3) = 63.9 kg, about 10 st 1 lb.

Family background

Why the range can be lower

NICE advises a lower BMI threshold for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, because health risks such as type 2 diabetes rise at a lower BMI. Overweight then starts at 23 rather than 25, so the healthy range is 18.5 to 22.9. At 5 ft 8 in that is 55.2 to 68.3 kg rather than 55.2 to 74.3 kg. Add your weight now to see where you sit; it is a starting point for a chat, never a verdict.

A bit of history

Made for medicine doses, not mirrors

Ben Devine wrote his formula in 1974 to help work out doses of the antibiotic gentamicin. The others were tweaks to fit later data. None of them was meant to be a weight to aim for, which is why we show the NHS BMI range as the main answer.

Read with care

What this cannot tell you

Your buildOnly height and sex go in, so a broad frame and a slight one get the same number.
Under 5 ftThe formulas start at 5 ft and say nothing useful below it.
HealthThey predate most of what we know about weight and health.

Questions

Common questions

Which ideal weight formula is most accurate?

None is a clear winner. Robinson and Miller tend to give lower answers for taller men, Devine and Hamwi higher ones. The average and the BMI each implies are shown so you can compare them side by side.

Which ideal weight formula is most accurate?

None of them is accurate in the sense of telling you what you should weigh. A 2000 review found they give quite different answers, especially for shorter and taller people. The NHS BMI range is the better guide.

Why does my ideal weight differ from my BMI range?

The formulas give one number each, while BMI gives a range. Most formula answers land inside the healthy BMI range, which is reassuring.

What is the ideal weight for a 5 ft 8 in woman?

The formulas give about 9 st 12 lb to 10 st 1 lb. The NHS healthy range for that height is 8 st 10 lb to 11 st 10 lb.

Sources

Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.

If your weight is on your mind

Talk to your GP if your weight has changed a lot without trying, or if it is worrying you. If food or your body feels hard to think about, Beat has a free helpline on 0808 801 0677 (England, weekdays 3pm to 8pm).