Free tool

BMI calculator

Q: What is BMI?

BMI (Body Mass Index) is your weight divided by your height squared. It's a quick, population-level screening number used by health organizations, but it doesn't distinguish between muscle and fat — it only knows total weight.

Q: Is BMI accurate for muscular people?

No. BMI can't tell the difference between muscle and fat, so a heavily muscled, lean person can score as 'overweight' or 'obese' on BMI despite having very little body fat. It was designed as a population-level statistical tool, not an individual body-composition measurement.

Q: What is a normal BMI range?

The standard WHO reference ranges are: under 18.5 is classified underweight, 18.5-24.9 normal, 25-29.9 overweight, and 30+ obese. These are population screening categories, not individual health verdicts.

Q: What should I use instead of BMI if I lift weights?

FFMI (Fat-Free Mass Index) accounts for body fat and reflects actual muscle mass, making it far more useful for anyone training seriously. A photo-based body composition grade goes further, breaking results down by individual muscle group.

Instant, free, no signup. And below it: the honest part most BMI calculators skip — what this number actually can and can't tell you.

Height

Weight

BMI

—

What BMI actually measures

BMI is your weight divided by your height squared. That's it — it has no idea what your weight is made of. It was designed in the 1830s as a population-level statistical tool, not a way to assess any one individual's body composition.

For most people who don't lift, it's a rough, usable screening number. For anyone with meaningful muscle mass, it starts breaking down fast.

Where it falls apart

A 100kg powerlifter at 12% body fat and a 100kg out-of-shape person at 35% body fat get the exact same BMI. Same formula, same number, completely different bodies. BMI can't see the difference because it was never built to.

No muscle vs. fat distinction — the single biggest blind spot, and the one that matters most if you train.
No frame or distribution awareness — where the weight sits on you isn't part of the equation.
Built for population averages — genuinely useful for public health statistics across millions of people, much less useful for judging one specific person.

Standard BMI ranges

<18.5Underweight — WHO reference category.

18.5–24.9Normal — WHO reference category.

25–29.9Overweight — WHO reference category.

30+Obese — WHO reference category.

These are population screening categories from the World Health Organization — not an individual medical verdict, and not adjusted for muscle mass, frame, or anything else about your specific body. Not medical advice.

What to use instead, if you lift

If BMI is telling you something that clearly doesn't match the mirror, it's not lying — it's just the wrong tool. FFMI accounts for body fat and actually reflects muscle mass. And for the full picture — muscle-by-muscle, not one blended number — a photo-based grade breaks it down properly.

Get a real breakdown — free One photo, graded S to E. No card.

Questions

What is BMI?

BMI (Body Mass Index) is your weight divided by your height squared. It's a quick, population-level screening number used by health organizations, but it doesn't distinguish between muscle and fat — it only knows total weight.

Is BMI accurate for muscular people?

No. BMI can't tell the difference between muscle and fat, so a heavily muscled, lean person can score as "overweight" or "obese" on BMI despite having very little body fat. It was designed as a population-level statistical tool, not an individual body-composition measurement.

What is a normal BMI range?

The standard WHO reference ranges are: under 18.5 is classified underweight, 18.5-24.9 normal, 25-29.9 overweight, and 30+ obese. These are population screening categories, not individual health verdicts.

What should I use instead of BMI if I lift weights?

FFMI (Fat-Free Mass Index) accounts for body fat and reflects actual muscle mass, making it far more useful for anyone training seriously. A photo-based body composition grade goes further, breaking results down by individual muscle group.

One number isn't the full story

Get a breakdown that actually knows what it's looking at.

Get your grade — free