⚖️ BMI Calculator
BMI = weight (kg) ÷ height² (m)
to calculate BMI
Frequently Asked Questions
How do I use the BMI Calculator?
Choose Metric (kg/cm) or Imperial (lb/ft-in) units, then enter your weight and height. The calculator updates instantly, showing your BMI value, weight category, and where you fall on the visual BMI scale from underweight to obese.
How is BMI calculated?
BMI = Weight (kg) / [Height (m)]². For imperial units, BMI = 703 × Weight (lb) / [Height (in)]². For example, a 70 kg person who is 1.75 m tall has a BMI of 22.9, which falls in the normal weight range.
What is a healthy BMI range?
A BMI between 18.5 and 24.9 is considered normal weight. Below 18.5 is underweight, 25.0–29.9 is overweight, and 30.0 and above falls into the obese categories (Class I, II, III).
Is BMI accurate for everyone?
BMI is a useful screening tool but doesn't account for muscle mass, bone density, age, sex, or fat distribution. Athletes and very muscular individuals may show a high BMI despite having low body fat. It's best used alongside other health indicators.
Does BMI calculation differ for children?
Yes — for children and teens, BMI is interpreted using age- and sex-specific percentile charts rather than the fixed adult categories shown here. This calculator's ranges apply to adults.
How do I convert my height and weight to metric units?
Use our Unit Converter to convert between kg/lb and cm/ft-in before entering your values here.
Why might BMI be misleading for older adults?
As people age, they tend to lose muscle mass and gain fat even if their weight stays the same, so a BMI in the "normal" range can mask reduced muscle strength (sarcopenia). Some guidelines suggest a slightly higher BMI (around 23–28) may be acceptable for adults over 65.
Does BMI account for waist size or fat distribution?
No — BMI only uses height and weight, so it can't distinguish between someone who carries fat around the waist (linked to higher health risk) and someone with the same BMI but a different fat distribution. Waist circumference or waist-to-hip ratio is often used alongside BMI for a fuller picture.