BMI Calculator
Check your Body Mass Index, see which weight category you fall into, and find the healthy weight range for your height.
Fill in your details and your BMI appears here instantly.
Your BMI
-
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
What is BMI?
Body Mass Index is your weight divided by the square of your height: BMI = kg / m² (or
703 × lb / in²). It is a screening tool, not a diagnosis – it flags weight categories
linked to health risk across populations, cheaply and instantly.
Where BMI falls short
BMI cannot tell muscle from fat. A muscular athlete can land in "overweight" with low body fat, and someone with little muscle can sit at a "healthy" BMI while carrying excess fat. Waist circumference and body-fat percentage add the context BMI misses. For most non-athletes, though, it tracks risk well enough to be the standard first check used by the CDC and WHO.
What to do with your result
If your BMI is outside the healthy range, the practical next step is a calorie plan: run the TDEE calculator to find your maintenance calories, then use the calorie deficit calculator or macro calculator to set daily targets.
BMI categories for adults
The CDC groups adult results into four main categories, the same ones this calculator shows with your result:
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5 to less than 25 |
| Overweight | 25 to less than 30 |
| Obesity | 30 or above |
These cutoffs are the same for men and women and apply from age 20. Under 20, weight is assessed with age- and sex-specific percentile charts instead.
How to work out BMI by hand
Metric example: at 70 kg and 1.75 m, divide 70 by 1.75 squared (3.06) and you get 22.9.
Imperial example: at 154 lb and 5 ft 9 in (69 inches), multiply 154 by 703, then divide by 69 squared (4,761) and you get 22.7. Both results land in the healthy band.
The healthy weight range in your result
Alongside your BMI, the calculator converts the healthy band into a weight range for your height, shown in both kilos and pounds. Treat it as a band rather than a bullseye: health does not sit at one exact weight, and where you feel and perform well inside the range is personal.
Frequently asked questions
What is a healthy BMI?
18.5 to 24.9 is classed as healthy weight for adults. Below 18.5 is underweight, 25-29.9 overweight, and 30 or above obese.
Is BMI accurate for athletes?
No – it overestimates fatness in muscular people. If you lift regularly, treat BMI as a rough screen and use body-fat measurements or progress photos instead.
Does BMI apply to children and teens?
Not with these adult cutoffs. Children are assessed with age- and sex-specific percentile charts – this calculator is for adults only.
Why does this calculator ask for age and sex?
BMI is worked out from height and weight only, so those two entries never change your result. Age and sex do matter on the other calculators on this site, like the TDEE and BMR tools, whose equations use them.
How often should I check my BMI?
There is no fixed rule. Rechecking after your weight changes by a few kilos is enough for most people. A single reading matters less than the direction it moves over months.
Does this calculator use metric or imperial units?
Both. Use the Units toggle at the top of the calculator to switch between imperial (feet/inches and pounds) and metric (centimetres and kilograms). The healthy weight range in your result is shown in both kilos and pounds either way.
Disclaimer
BMI is a screening tool, and this page is general information, not medical advice or a diagnosis. If your result concerns you, or you are pregnant, under 18, or managing a health condition, talk to a doctor about what the number means for you.