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Utlty

Health

BMI, calories, body fat, due dates and daily water.

Body

Nutrition

Pregnancy

About health

The health calculators turn a few measurements into the numbers people ask about most: body mass index with the WHO categories and the lower cut-offs used for South Asian adults, daily calories from the Mifflin-St Jeor equation, body fat from tape measurements with the US Navy method, a pregnancy due date from the last period, conception or an IVF transfer, and a daily water estimate.

Each page names its formula and links the guidelines and studies its thresholds come from, with the date they were checked. The results are estimates for adults, not a diagnosis: bodies vary, and a doctor, dietitian or midwife can tell you what your numbers mean for you.

Questions

Are BMI cut-offs different for Indians and other South Asians?

Yes. Because health risks rise at a lower BMI, NICE uses overweight from 23 and obesity from 27.5 for people of South Asian background, and the 2009 Indian consensus statement uses overweight from 23 and obesity from 25. The BMI calculator shows these alongside the WHO categories.

How accurate are these calculators?

As accurate as the published formulas behind them, which describe averages, so your own figure can be off. In one study of army recruits the US Navy tape method read about 6 percentage points below a DXA scan, and a due date worked out from a period is a first estimate that an early ultrasound scan may change.

Can I use them for children or during pregnancy?

Only the due date calculator is meant for pregnancy. The BMI, calorie, body fat and water calculators use adult formulas: children need age-specific growth charts, and pregnancy changes weight, calorie and water needs, so ask your doctor or midwife.