BMI Calculator
Find your Body Mass Index (BMI) and category from your height and weight. BMI is a quick screening tool, not a diagnosis.
BMI is a screening tool, not a diagnosis. It doesn't account for muscle mass, bone density or body composition — talk to a healthcare professional for a full picture.
BMI categories
Want a more useful number?
Your TDEE tells you how many calories to eat — try the TDEE calculator next.
Try the TDEE calculatorWhat BMI is (and isn't)
Body Mass Index (BMI) is a simple screening measurement calculated from your height and weight. In metric units, it's BMI = weight(kg) ÷ height(m)²; in imperial units, this calculator uses the equivalent formula BMI = 703 × weight(lbs) ÷ height(in)². The result places you into one of four standard categories: underweight (below 18.5), normal weight (18.5–24.9), overweight (25.0–29.9), or obese (30.0 and above).
BMI became popular because it's cheap and easy to calculate at a population level — public health researchers use it to track weight trends across large groups of people. But at the individual level, it has real limitations. BMI only looks at total body weight relative to height; it has no way to tell the difference between fat mass and muscle mass. A muscular athlete and a sedentary person of the same height and weight can have identical BMI scores despite very different body compositions. BMI also doesn't account for bone density, age-related changes in body composition, sex differences in typical body fat percentage, or where fat is distributed on the body (which matters for health risk).
That's why BMI is best treated as a quick screening tool, not a diagnosis. If your BMI falls outside the "normal" range, it's a reasonable prompt to look closer — but it shouldn't be the only number you use to judge your health, and it definitely shouldn't be a source of anxiety on its own. A doctor or registered dietitian can combine BMI with other measurements (waist circumference, body composition testing, blood work, family history) to get a much fuller picture.
When to use TDEE and calorie tracking instead
If your actual goal is to lose, gain, or maintain weight, BMI won't help you get there — it's a snapshot, not a plan. What you actually need is your TDEE (Total Daily Energy Expenditure), which estimates how many calories your body burns in a day, and a sensible calorie target based on that number. From there, consistent tracking — of your food intake, and of your weight trend over time — is what actually tells you whether your plan is working, because it reflects your real body's real response, not just a formula.
CalorieToday is built for exactly this: log your food and weight, see your trend over weeks instead of single noisy days, and let your calorie target adjust automatically as your weight actually changes.