BMI Calculator
A free, accurate BMI calculator for men and women — enter your height and weight in either metric (kg, cm) or imperial (lb, ft/in) units to instantly see your body mass index, your healthy weight range, and your BMI Prime. Choose Male or Female for sex-specific body-fat context, calculated with the same formula used by the CDC and NIH.
Reviewed for accuracy: January 2026 · Written and reviewed by Manzoor Ahmad, Pharmacist · Formula sourced from CDC.gov and NHLBI, NIH
This works as both a BMI calculator male and BMI calculator female option — the formula is identical either way, but the typical body-fat-range context on the right adjusts to match your selection.
BMI Chart for Adults
These are the standard BMI categories used by the World Health Organization and the CDC for adults aged 20 and over, alongside the tighter cut-offs recommended for people of South and East Asian descent, who tend to carry more body fat at the same BMI as other populations.
| Category | General BMI Range | Asian Cut-off Range |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Normal weight | 18.5 – 24.9 | 18.5 – 22.9 |
| Overweight | 25.0 – 29.9 | 23.0 – 24.9 |
| Obese Class I | 30.0 – 34.9 | 25.0 – 29.9 |
| Obese Class II | 35.0 – 39.9 | 30.0 and above |
| Obese Class III | 40.0 and above |
How to Calculate BMI Manually
If you want to check your body mass index by hand rather than relying on a BMI calculator, the formula is straightforward — it’s the same equation the calculator above runs every time you move a slider. It was originally devised in the 1830s by the Belgian mathematician Adolphe Quetelet, which is why BMI is still sometimes called the “Quetelet Index.”
Metric BMI formula (kg, cm)
BMI = weight (kg) ÷ [height (m)]²
Example: a person who weighs 70 kg and is 170 cm (1.70 m) tall has a BMI of 70 ÷ (1.70 × 1.70) = 70 ÷ 2.89 = 24.2.
Imperial BMI formula (lb, in)
BMI = 703 × weight (lb) ÷ [height (in)]²
Example: a person who weighs 154 lb and is 5 ft 7 in (67 in) tall has a BMI of 703 × 154 ÷ (67 × 67) = 108,262 ÷ 4,489 = 24.1.
Whichever unit system you use, the underlying math is identical — the imperial version simply bundles the 2.2-lb-to-kg and inch-to-metre conversions into that constant 703. If you’d rather skip the manual calculation, enter your numbers in the BMI calculator kg and cm fields (or the pounds and inches fields) above and the result updates as you type. Want a bmi calculator kg with age built in? Open Advanced options above — your age doesn’t change the formula, but it does change how the result should be read.
Is BMI Accurate for Everyone?
BMI is a fast, free screening tool — not a diagnosis — and it’s worth understanding where it holds up and where it doesn’t before you read too much into a single number.
Men and women use the same formula
There’s no separate BMI calculator formula for men and women — the calculation and category cut-offs are identical for adult men and women. That said, at the same BMI, women typically carry a somewhat higher percentage of body fat than men, which is one reason doctors often pair BMI with a waist-to-hip ratio or body fat percentage reading.
Muscular and athletic bodies can be misread
Because BMI only looks at total weight relative to height, it can’t tell muscle from fat. A muscular BMI calculator result — say, a rugby player or powerlifter landing in the “overweight” range — is a well-known limitation. If that sounds like you, our Body Fat Percentage Calculator or Lean Body Mass Calculator will give you a much clearer picture.
Ethnicity changes the healthy range
People of South and East Asian descent tend to develop weight-related health risks at lower BMI thresholds than the general WHO cut-offs suggest, which is why an Asian BMI calculator toggle — like the one above — typically shifts “overweight” down to 23 instead of 25.
Not intended for children, teens, or pregnancy
This adult BMI calculator applies to people aged 20 and over. Children and teens are assessed against age- and sex-specific growth-chart percentiles instead — use our Child BMI Percentile Calculator for anyone under 20. BMI is also not a reliable measure during pregnancy or for older adults who have lost significant muscle mass.
Explore More Health Calculators
BMI is just one piece of the picture. These related tools from our full health calculators library dig deeper into body composition, growth, and clinical dosing measures.
Frequently Asked Questions
For most adults, a BMI between 18.5 and 24.9 falls in the normal (healthy) weight range, regardless of height — that’s the point of BMI, it already adjusts for height. Enter your numbers in the calculator above to see your exact healthy weight range in kilograms or pounds.
No — the BMI formula and standard category cut-offs are the same for adult men and women. Doctors sometimes look at additional measures like waist-to-hip ratio alongside BMI because women tend to carry more body fat than men at an identical BMI value.
Less accurate than for the general population. Since BMI can’t distinguish muscle from fat, athletes and heavily muscled people are often flagged as “overweight” despite having low body fat. A body fat percentage or lean body mass calculation gives a more reliable picture in that case.
Many public health bodies recommend it. Research shows people of South and East Asian descent tend to face higher health risks at lower BMI values than the general WHO cut-offs suggest, so the “Asian cut-offs” toggle in the calculator above shifts overweight down to a BMI of 23 instead of 25.
BMI Prime is your BMI divided by 25 (the upper edge of the normal range). A BMI Prime under 0.74 suggests underweight, 0.74–1.00 is the normal range, and anything above 1.00 indicates overweight — it’s a quick, unit-independent way to see how far your weight sits from the healthy ceiling.
The math is the same weight-over-height-squared formula, but the result isn’t compared to fixed adult categories. Instead, it’s plotted on a sex- and age-specific growth chart to produce a percentile. Use our Child BMI Percentile Calculator for anyone under 20.
Both. The BMI formula itself is identical for men and women, so selecting Male or Female above won’t change your BMI number — but it will switch the “typical body fat” reference shown next to your result to the sex-specific ACE range, since men and women carry different amounts of body fat at the same BMI.
Yes. Stay on Metric units to enter your weight in kilograms, then open “Advanced options” above to add your age. Age doesn’t change the BMI formula, but it does change how you should interpret the result — the calculator will flag if you’re under 20 (use the Child BMI Percentile Calculator instead) or 65+ (where muscle loss can affect what BMI means for you).
References
- Centers for Disease Control and Prevention. About Body Mass Index (BMI). CDC.gov, 2025.
- Centers for Disease Control and Prevention. Adult BMI Categories. CDC.gov.
- National Heart, Lung, and Blood Institute, National Institutes of Health. Calculate Your BMI. NHLBI.NIH.gov.
- World Health Organization. Body Mass Index (BMI). Global Health Observatory, WHO.int.
- World Obesity Federation. Obesity Classification. WorldObesity.org.
- Cleveland Clinic. Body Mass Index: What It Is, Limitations & BMI Calculator. ClevelandClinic.org.
- Johns Hopkins Medicine. BMI Calculator. HopkinsMedicine.org.
- American Council on Exercise (ACE). Percent Body Fat Norms for Men and Women. Referenced via ACEfitness.org.