BMI Calculator
Calculate your body mass index (BMI) and see your WHO weight category instantly. BMI is a quick screening tool that compares your weight to your height - this calculator also shows the healthy weight range for your height so you know your target.
How This Calculator Works
BMI is calculated as weight(kg) / height(m) squared. The World Health Organization groups adults into categories: below 18.5 is underweight, 18.5-24.9 is the healthy range, 25-29.9 is overweight, and 30 or above is obese.
BMI is a screening tool, not a diagnosis. It measures how heavy you are for your height, but not what that weight is made of - muscle and bone are denser than fat. This is why muscular lifters often score "overweight" while carrying little fat, and why BMI applies less well to adults over 65, children, and pregnant women.
For most people, though, BMI tracks closely with body fat and health risk. If your BMI is above 25 and your waist is also large (over 94 cm for men, 80 cm for women), the combination is a stronger signal than either number alone. Pair this tool with our body-fat calculator for a fuller picture.
References & Sources
Frequently Asked Questions
What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered the healthy range for adults by the WHO. Below 18.5 is underweight and above 25 is overweight, with 30 marking obesity. These thresholds apply to adults aged 20-65; older adults may do better slightly higher, around 23-28.
Is BMI accurate for muscular people?
Not really. BMI cannot tell muscle from fat, so very muscular people often score in the "overweight" range despite low body fat. If you lift regularly and your waist is slim, ignore a slightly high BMI and track body fat instead. For everyone else, BMI correlates well with health risk.
How do I calculate BMI by hand?
Divide your weight in kilograms by your height in meters squared. For example: 80 kg / (1.80 m x 1.80 m) = 24.7. If you use pounds and inches, multiply the result by 703: 176 lb / (71 in x 71 in) x 703 = 24.6.
What BMI should I aim for when losing weight?
If you are above the healthy range, aim to lose 5-10% of your body weight first - it delivers most of the health benefit even if your BMI stays technically "overweight". A weight inside the 18.5-24.9 range is the long-term target, approached at 0.5-1 kg per week to keep muscle.
Body Fat Calculator
Estimate your body fat percentage with nothing but a tape measure. This calculator uses the US Navy circumference method, which predicts body fat from neck, waist, and hip measurements - one of the most accurate field methods validated against lab testing.
TDEE Calculator (Daily Calories)
Calculate your Total Daily Energy Expenditure (TDEE) - the number of calories you burn each day. The calculator uses the Mifflin-St Jeor equation for your basal metabolic rate, multiplied by your activity level.
Macro Calculator
Calculate your daily macronutrient targets - protein, carbs, and fat - based on your body stats and goal. This calculator estimates your calorie needs with the Mifflin-St Jeor equation, then splits them into macros using research-backed protein ranges.
