BMI Calculator
Calculate your Body Mass Index from height and weight in either metric or imperial units.
How to use
- Choose metric or imperial units.
- Enter your height and weight.
- Your BMI and weight category appear instantly.
How the BMI Calculator works
Calculates Body Mass Index, a height-for-weight ratio used as a rough population-level screening figure for underweight, healthy weight, overweight and obesity.
In metric, BMI is weight in kilograms divided by height in metres squared. The imperial form multiplies by 703 to convert pounds and inches into the same scale.
metric: BMI = kg / m² imperial: BMI = 703 × lb / in²
Worked example
Someone 175 cm and 70 kg has a BMI of 70 / 1.75² = 22.9, which sits in the healthy range. The same person in imperial — 5'9" and 154 lb — gives 703 × 154 / 69² = 22.7.
Things worth knowing
- Standard categories: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30 and above obese.
- BMI cannot distinguish muscle from fat. Muscular athletes routinely score 'overweight' while carrying very little body fat.
- It also ignores fat distribution, which matters clinically — waist circumference is a better indicator of metabolic risk.
- The thresholds were derived largely from European populations; several health bodies use lower cut-offs for people of South and East Asian descent.
Frequently asked questions
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered the normal range.
Is BMI accurate for everyone?
BMI is a general screening tool and doesn't account for muscle mass or body composition, so athletes may read high.
Is body fat percentage better?
Generally yes, because it measures what BMI only estimates. It is harder to measure accurately without proper equipment.