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Health & Wellbeing2 min check
BMI Calculator
Step 1 of 10%
How it works
BMI = weight ÷ height². It's a population-level screening measure. The NHS uses standard thresholds for general adults and lower thresholds for ethnicities at higher cardiometabolic risk at the same BMI (South Asian, Chinese, African-Caribbean).
Worked example
1.75m, 75kg → BMI = 75 ÷ (1.75 × 1.75) = 24.5 → Healthy weight (general thresholds).
Who should use this
- •Adults 18+ wanting a quick weight-status indicator
- •People starting a weight management plan
- •Anyone tracking changes over time
Common mistakes
- ×Using BMI for very muscular people (over-classifies as overweight)
- ×Using adult BMI on children (use BMI centile charts instead)
- ×Forgetting ethnicity-specific thresholds
- ×Treating BMI as a single source of truth rather than alongside waist size
Frequently asked questions
Is BMI accurate for athletes?▾
Often not — high muscle mass can push BMI into overweight while body fat is low and healthy.
What's a healthy BMI?▾
18.5–24.9 for general adults, 18.5–22.9 for South-Asian, Chinese and African-Caribbean adults.
Should I use BMI for my child?▾
No — children use BMI percentile charts that account for age and sex.
Does BMI predict health risk?▾
Roughly. Waist circumference, blood pressure, cholesterol and HbA1c add much better picture.