Free Tools
BMI Calculator
Enter your height and weight for an instant Body Mass Index and category — in metric or imperial. Then read the part most BMI calculators leave out: why the number misjudges anyone who trains.
No sign-up, no maths. BMI is a fast population screen, but it cannot tell muscle from fat — so we point you straight to the body fat and FFMI tools that actually measure a physique.
Enter your height and weight to see your BMI — then use the better tools below.
Body composition tool
Body Fat Calculator
What BMI cannot see: estimate how lean you actually are from a tape measure.
Body composition tool
FFMI Calculator
The muscle-aware version of BMI — scores your lean mass for your height.
What BMI actually is
Body Mass Index is a nineteenth-century formula: your weight divided by your height squared. It was built to describe populations, not individuals, and it does that job cheaply — no equipment, one quick sum. As a rough flag at the extremes it still works. The trouble starts the moment you use it to judge one person, because a single number from weight and height alone cannot describe a body.
Why lifters read "overweight"
Muscle is denser than fat, so a trained lifter carries more weight for their height than the sedentary average the BMI bands were calibrated on. The result is that most people with a serious training age land in the overweight band, and plenty of lean, competition-ready physiques read as obese. The formula is not wrong about your weight — it is simply blind to what that weight is made of. That single blind spot is why BMI and a photo of the same person often tell completely different stories.
The numbers to trust instead
If you train, two figures beat BMI outright. Body fat percentage tells you how lean you are, which is what "overweight" is really trying to get at. FFMI tells you how much muscle you carry for your height, which is what makes a lifter heavy in the first place. Measure both and BMI becomes a footnote: you will know whether your weight is fat to lose or muscle to be proud of, and no population average can argue with that.
Common questions
How is BMI calculated?+
BMI is your weight in kilograms divided by your height in metres squared. So an 82kg person at 1.78m has a BMI of 82 / (1.78 x 1.78), which is about 25.9. If you work in pounds and feet, we convert for you — the maths and the resulting number are exactly the same on either unit system.
What is a healthy BMI?+
For the general adult population the World Health Organisation bands are: under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, and 30 or above obese. These are population averages built from people who mostly do not lift, so treat them as a rough screen rather than a verdict on your individual health.
Why is BMI inaccurate for muscular people?+
BMI only knows your total weight and your height. It cannot tell whether that weight is muscle or fat, so a lean, heavily trained lifter and a soft, sedentary person of the same height and weight get the identical BMI. Because muscle is dense, most serious lifters read as overweight or even obese on BMI while carrying perfectly healthy body fat. That is a limitation of the formula, not a problem with your physique.
What should lifters use instead of BMI?+
Body fat percentage and FFMI (Fat-Free Mass Index) are far better. Body fat percentage tells you how lean you actually are, and FFMI scores how much muscle you carry for your height. Together they separate the two things BMI blurs into one. Both have free calculators on this site, and a tape measure is enough to get started.
Is BMI completely useless then?+
No. As a quick, zero-equipment population screen it still has a place, especially at the extremes and for people who do not train. It is simply the wrong tool for judging a muscular physique. Use it as a starting point, then reach for body fat percentage or FFMI for anything that matters to a lifter.
Is this medical advice?+
No. BMI and the body-composition tools here are general, evidence-based estimates for healthy adults, not clinical assessment or medical advice. If you have a health condition or concerns about your weight, speak to a qualified clinician.
Past the number — build the body
BMI does not move a physique; training, protein and consistency do. The two supplements with real evidence behind them — whey to hit your protein target and creatine to support the work — are each scored 0–100 on how closely they match that evidence.
Informational only — not medical advice. BMI bands are population averages and do not account for muscle mass. Buy links are affiliate links; we may earn a commission at no extra cost to you.