How to Calculate BMI
The formula in metric and imperial, with worked examples — weight ÷ height², or 703 × weight ÷ height². Or enter your numbers below to skip the maths.
Calculate BMI
Range: 30–300 kg · up to 2 decimals
Enter your height in centimeters (e.g., 170 cm)
South, East or Southeast Asian — applies WHO 2004 adjusted thresholds
*This calculator is for informational purposes only. Please consult a healthcare professional before making any health decisions. See our medical disclaimer for more information.
Calculations are powered by the WHO BMI Classification System, the global standard for weight category assessment.
Quick Answer
The BMI Formula
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lb) ÷ height (in)². Both routes reach the same number. For 80 kg at 1.8 m, that is 80 ÷ 3.24 = 24.7. The calculator above runs either version and adds your category — but the arithmetic is simple enough to do by hand.
Calculating BMI in Metric
Take your weight in kilograms and your height in metres. Square the height — multiply it by itself — then divide your weight by that figure. A person of 80 kg standing 1.80 m tall works out as 1.80 × 1.80 = 3.24, then 80 ÷ 3.24 = 24.7. A BMI of 24.7 sits just inside the normal range, which runs from 18.5 up to but not including 25. If your height is in centimetres, divide it by 100 first: 175 cm becomes 1.75 m.
Calculating BMI in Pounds and Inches
The imperial version adds one constant. Multiply your weight in pounds by 703, then divide by your height in inches squared. Someone of 176 lb at 71 inches (5 ft 11) computes as 703 × 176 = 123,728, then 71 × 71 = 5,041, and 123,728 ÷ 5,041 = 24.5. The 703 factor is just the unit conversion that makes pounds-and-inches land on the same kg/m² scale as the metric formula — it is not a separate “imperial BMI”. Once you have the number, read it against the categories: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30 and over obese.
To skip the arithmetic, enter your figures in the calculator above — it handles metric, imperial and stones and shows your category and healthy weight range. From there, the Weight Loss Calculator turns a goal into a daily calorie target and the TDEE Calculator estimates your daily burn. For Asian and senior thresholds, use the parent BMI Calculator.
Children and teens (2–19) are assessed on age- and sex-specific BMI percentiles rather than the fixed adult formula. BMI is a screening figure, not a measure of body fat.
Precision Tracking Tools
Monitor your baseline metrics with clinical accuracy to ensure you stay on target.
Custom Meal Design
Access foundational dietary blueprints structured for sustainable, long-term success.
Expert Coaching
Connect with certified professionals who can tailor strategies to your unique physiology.
Explore More Tools
Each calculator feeds into the next — your data carries forward automatically through every step.
BMI
Establish your baseline with Asian and senior-adjusted thresholds for clinical accuracy beyond a generic scale.
Weight Loss
How many calories to eat to lose weight — your maintenance, daily target, the deficit, and a realistic timeline to your goal.
TDEE
Find out exactly how many calories your body burns daily — the foundation of every weight loss plan.