UK Health Calculators

The NHS uses the same WHO BMI ranges: under 18.5 is underweight, 18.5–24.9 is healthy weight, 25–29.9 is overweight, and 30 or above is obese. For people of South Asian, Chinese, Black African or Caribbean background, the NHS recommends lower thresholds — healthy weight is typically considered below 23. BMI is a screening tool, not a diagnosis.

TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day, accounting for your basal metabolic rate and your activity level. It is calculated by first working out your BMR using the Mifflin-St Jeor equation (which accounts for height, weight, age and sex), then multiplying by an activity factor from sedentary to very active.

BMI is a useful population-level screening tool but has well-documented limitations. It does not distinguish between muscle and fat mass, which means highly muscular people can show as overweight. It also does not account for where fat is distributed — waist circumference is a better predictor of metabolic risk. The NHS recommends using BMI alongside waist measurement for a more complete picture.

No. These calculators produce estimates based on standard clinical formulas and are for general awareness only. They are not a diagnosis and do not replace a consultation with your GP, a registered dietitian, or another qualified health professional. If you have concerns about your weight or health, speak to your doctor.