Muscle and sport
High muscle mass can raise your BMI without any extra body fat behind it. Pair the result with % body fat or tape measurements.
BMI calculator — your score and what to check next
Enter your weight and height — you'll get your BMI, healthy range, and a nudge on what to check next when the number alone isn't the whole story.
BMI is a quick screening ratio, not a diagnosis. It can't tell muscle from fat and tends to be less reliable for athletes, older adults, during pregnancy, or in children. Not sure what it means for you? Ask a doctor — don't lean on the number alone.
Result
Enter data and click Calculate.
How results are calculated
BMI = weight (kg) ÷ height (m)².
BMI = 703 × weight (lb) ÷ height (in)².
The healthy weight range is mass for BMI 18.5–24.9 at your height (from 18.5×height² to 24.9×height²) — shown in header units.
WHO bands: <18.5 underweight · 18.5–24.9 normal · 25–29.9 overweight · 30–34.9 obesity I · 35–39.9 obesity II · ≥40 obesity III.
BMI categories at a glance
Five WHO adult bands — the same split you see in the silhouettes below. Once you calculate, we'll highlight the one that matches your result.
Weight is low for height. Worth reviewing diet and causes with a clinician.
The band most people call "healthy weight" for adults.
Higher weight for height — a good moment to look at food and movement.
WHO classes I and II. Risk climbs here — a check-up makes sense.
The highest screening band — plan care together with a doctor.
How to read your BMI
BMI sorts adults by weight relative to height. It's a screening tool: it shows which WHO band you land in — not whether you're "healthy" or "ill".
What BMI does well
It gives researchers a shared language and gives you a quick map: underweight, normal, overweight, obesity. Across large groups it works reasonably well.
What BMI doesn't do
It doesn't measure fat, see muscle, or know your age or whether you're pregnant. One number can't replace labs or a conversation with a clinician.
Where the healthy weight range comes from
For your height we compute the mass that matches BMI 18.5 and 24.9 (BMI 18.5–24.9). That's exactly the span shown as the healthy weight range.
It's orientation, not a personalized target. A muscular, older, or recovering person can sit outside the band for good reasons — and the reverse can be true too.
BMI vs muscle, age, pregnancy, and kids
Age
In older adults, body composition and risk patterns look different from a 30-year-old's. BMI is only one signal, not the whole story.
Pregnancy
Adult cut-offs aren't a pregnancy assessment. What matters is the rate of weight gain — that's why there's a dedicated calculator for it.
Children and teens
They need age- and sex-specific percentiles instead. This tool is built for adults.
BMI vs other metrics
BMI only answers one question: weight relative to height. These three tools answer different ones — and they're often the better "what next".
BMI vs body fat
What it measures: BMI — weight for height. Body fat % — an estimate of fat share from tape measurements.
When it helps: if you lift, you're showing a "high" BMI while feeling fit, or you just want to know whether your weight is mostly muscle.
What it misses: BMI can't tell fat from muscle. Body-fat estimates are still estimates, not a DXA scan.
Calculate body fat →BMI vs BMR
What it measures: BMR — a rough resting calorie need.
When it helps: when you're planning food, want an energy baseline, or you're comparing diet phases.
What it misses: BMR doesn't judge whether your BMI is "good", and it ignores training load.
Calculate BMR →BMI vs TDEE
What it measures: TDEE — daily energy with activity (usually BMR × activity factor).
When it helps: when you want to maintain, build, or reduce weight without guessing calories.
What it misses: TDEE doesn't score your BMI category and doesn't replace clinical care.
Calculate TDEE →In short
- Enter weight and height in the header units.
- Read your BMI, category, and the healthy range (18.5–24.9).
- Check out "what to check next" — body fat, BMR/TDEE, or the hub below.
Real-world examples
Three categories — three different "what next" panels. Card units follow the header (kg/cm or lb/in).
Underweight — smaller frame
- Weight: 48 kg
- Height: 170 cm
BMI ~16.6 — underweight
The panel points to body-composition context plus protein/TDEE — not just the label.
Normal weight — shorter height
- Weight: 52 kg
- Height: 162 cm
BMI ~19.8 — normal weight
Inside the WHO band, but the panel still points to body fat, protein, and water as useful next checks.
Overweight — active lifter
- Weight: 92 kg
- Height: 180 cm
BMI ~28.4 — overweight
The label can be misleading with strength training — the panel leads with body fat, then BMR and TDEE.
FAQ
How accurate is BMI, really?
Fine as a quick screen. Weak as a body-composition measure. It only ratios weight to height, so it can't see muscle vs fat. It sorts risk well for populations; for you it can mislead.
I lift weights — does BMI still work?
It often overstates things. Muscle is denser than fat, so a lean lifter can land in “overweight.” Add a body-fat estimate (e.g. Navy) or simple waist measures.
What BMI counts as healthy?
For adults, usually 18.5–24.9. That's a WHO screening band, not a health scorecard. Below 18.5 is underweight, 25–29.9 overweight, 30+ obesity classes.
Can BMI give me an “ideal” weight?
You can back out the weight band for BMI 18.5–24.9 at your height — that's the healthy range in the result. It isn't a personalized medical target or a physique guarantee.
Why is the healthy weight range only a guide?
Because it only knows height and fixed BMI cutoffs. It doesn't know age, sex, composition, conditions, or lifestyle. Treat it like a map, not turn-by-turn directions.
What about kids and teens?
They use age- and sex-specific percentile charts. This calculator is for adults.
Does BMI make sense in pregnancy?
Adult cutoffs aren't a pregnancy diagnostic. What matters is gain pace relative to pre-pregnancy BMI — try the pregnancy weight-gain calculator and talk with your doctor.
What else should I check besides BMI?
Waist size, a body-fat estimate, BMR/TDEE if you're planning calories, how you feel, sleep, and labs your doctor orders. BMI is a starting point, not your full health report.
Related health calculators
BMI is a solid start. These tools answer the next questions: body composition, daily needs, and the cases where adult BMI cut-offs just don't fit.