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BMI Calculator — Check Your Body Mass Index in 2 Seconds

Enter your height and weight, get your BMI number plus WHO category instantly. Works in metric or imperial, runs in your browser, and we don't store anything. But read the fine print below — BMI is a useful starting point, not a diagnosis.

BMI Calculator

BMI Calculator

Calculate your Body Mass Index
Your Measurements
Enter your body measurements
Your Results
BMI and health category
Enter measurements and click Calculate
BMI Categories
World Health Organization (WHO) Guidelines
ClassificationBMI Range
Severe Thinness< 16
Moderate Thinness16 - 17
Mild Thinness17 - 18.5
Normal Weight18.5 - 25
Overweight25 - 30
Obese Class I30 - 35
Obese Class II35 - 40
Obese Class III> 40
About BMI

Body Mass Index (BMI) is a simple and widely used method for assessing body weight relative to height. It is calculated by dividing weight in kilograms by height in meters squared (kg/m²).

BMI is a general indicator of whether a person has a healthy body weight. It is used by healthcare professionals as a screening tool to identify potential weight-related health risks.

Key Features:

  • Supports both metric (kg/cm) and imperial (lbs/inches) units
  • Instantly calculates BMI with high precision
  • Provides classification based on WHO guidelines
  • Shows ideal weight range for your height
  • Visual BMI scale indicator

What BMI Actually Measures (And What It Doesn't)

BMI is weight (kg) divided by height (m) squared. That's it — one division. The formula was invented by Adolphe Quetelet in 1832 (yes, almost 200 years ago) as a population-level statistical tool, not a personal health metric.

The WHO adopted it in the 1990s because it's cheap and fast to calculate. A BMI of 22 means you weigh 22 kg for every square meter of height. The "normal" range is 18.5–24.9, but this cutoff was set using data primarily from white European populations.

Here's what BMI cannot tell you: your body fat percentage, where fat is distributed (visceral vs subcutaneous), your muscle mass, bone density, or metabolic health. A 95 kg rugby player and a 95 kg sedentary office worker at the same height get the same BMI — but their health profiles are completely different. That said, for the general population, BMI correlates reasonably well with health outcomes at the extremes (< 18.5 and > 30).

When BMI Is Actually Useful

Quick health screening at annual checkups

Your doctor uses BMI as a first-pass filter. If it's between 20–25, they probably won't dig deeper into weight-related risks. If it's 32, they'll order blood work for metabolic syndrome markers. It's a triage tool, not a verdict.

Tracking weight trends over months

BMI is more useful as a trend line than a single number. Going from 27 to 24 over 6 months tells you something. A single reading of 26.1 on a Tuesday morning tells you almost nothing — water weight alone can swing BMI by 0.5–1.0 points.

Insurance and medical eligibility thresholds

Like it or not, many insurance companies and medical procedures use BMI cutoffs. Bariatric surgery typically requires BMI ≥ 40 (or ≥ 35 with comorbidities). Some life insurance premiums increase above BMI 30. Knowing your number helps you navigate these systems.

Population health research and epidemiology

BMI works well for studying large groups — correlating obesity rates with disease prevalence across countries. It falls apart for individuals, but across 10,000 people, the statistical signal is strong enough to be useful.

What Most BMI Calculators Won't Tell You

1.

Asian populations have different risk thresholds

WHO recommends lower cutoffs for Asian populations: overweight starts at 23 (not 25), and obesity at 27.5 (not 30). This is because Asian body types tend to carry more visceral fat at lower BMI values. If you're East or South Asian, a BMI of 24 may already indicate elevated metabolic risk.

2.

BMI is useless for athletes and muscular people

Muscle is denser than fat. A 180cm person with 15% body fat and significant muscle mass might have a BMI of 28 — "overweight" by the chart, but metabolically healthy. If you strength train 3+ times per week, use body fat percentage or waist-to-hip ratio instead.

3.

Waist circumference matters more than BMI for health risk

A waist measurement over 94cm (men) or 80cm (women) indicates elevated cardiovascular risk regardless of BMI. You can have a "normal" BMI of 23 but dangerous visceral fat if it's concentrated around your organs. Measure at your navel, standing relaxed.

4.

Don't use BMI for children or elderly

Children use age-and-sex-specific BMI percentiles (CDC growth charts), not adult cutoffs. For adults over 65, a slightly higher BMI (25–27) is actually associated with lower mortality — the "obesity paradox." The standard 18.5–24.9 range doesn't apply to either group.

Real Calculations

Average adult — metric

A 170cm, 68kg person (common in many countries).

Input

Height: 170 cm, Weight: 68 kg

Output

BMI = 68 / (1.70)² = 68 / 2.89 = 23.5 → Normal weight (WHO range: 18.5–24.9)

Muscular person — shows BMI limitation

A 180cm, 95kg person who lifts weights 4x/week with 14% body fat.

Input

Height: 180 cm, Weight: 95 kg

Output

BMI = 95 / (1.80)² = 95 / 3.24 = 29.3 → "Overweight" by BMI, but 14% body fat is athletic range. This is why BMI alone isn't enough for active people.

Features

  • Instant BMI calculation — no page reload needed
  • Supports metric (kg/cm) and imperial (lbs/inches) with one toggle
  • Shows WHO classification with color-coded scale
  • Displays ideal weight range for your height
  • Works entirely in your browser — no data sent anywhere
  • Free, no signup, no ads

Frequently Asked Questions

What BMI is considered obese in 2026?

WHO still uses BMI ≥ 30 as the obesity threshold for most populations. However, for Asian populations, the threshold is lower at 27.5. Some researchers argue these cutoffs are outdated and should be replaced with body fat percentage or metabolic health markers, but no official change has been made yet.

Is BMI different for men and women?

The formula is the same, and WHO uses the same cutoffs for both sexes. However, women naturally carry more body fat than men at the same BMI (about 10% more on average). A woman with BMI 24 typically has higher body fat percentage than a man with BMI 24. Some researchers advocate sex-specific ranges, but this isn't standard practice yet.

My BMI is 26 — should I worry?

Probably not, if you're otherwise healthy. A BMI of 26 is barely into the "overweight" range and within measurement noise (weigh yourself after a big meal vs. morning fasted — easily 1-2 kg difference). More important: How's your blood pressure? Fasting glucose? Waist circumference? If those are normal, a BMI of 26 is not a health emergency.

Why do bodybuilders have high BMI but low body fat?

BMI can't distinguish muscle from fat — it only knows total weight. Muscle is about 18% denser than fat. A bodybuilder at 180cm/100kg has BMI 30.9 ("obese") but might have 10% body fat. This is the most well-known limitation of BMI. If you have significant muscle mass, use a DEXA scan or skinfold calipers instead.

What's better than BMI for measuring health?

For individuals: waist-to-hip ratio (cardiovascular risk), body fat percentage via DEXA scan (gold standard), or even just waist circumference alone. For a free at-home check, measure your waist at the navel — over 94cm for men or 80cm for women signals elevated risk regardless of what BMI says.

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