GetHealthyCalculators
Skip to content

BMI Calculator

Body Mass Index (BMI) is a simple measure of body fat based on your height and weight. It applies to adult men and women and is used by healthcare professionals worldwide as a quick screening tool for weight categories that may lead to health problems.

Reviewed by GetHealthyCalculators Editorial Team · Updated April 14, 2026

Quick Answer

A healthy BMI is 18.5–24.9. Calculate yours by dividing your weight in kilograms by your height in meters squared.

These results are estimates based on general formulas and are not a substitute for professional medical advice. Consult a healthcare provider before making health decisions.

Enter your weight and height above to calculate your BMI.

How the Formula Works

  1. Measure your weight in kilograms. If using pounds, convert by multiplying by 0.453592.

    weight (kg) = weight (lbs) × 0.453592

  2. Measure your height in meters. If using feet and inches, convert to meters first.

    height (m) = (feet × 12 + inches) × 0.0254

  3. Square your height by multiplying it by itself.

    height² = height (m) × height (m)

  4. Divide your weight in kilograms by your squared height in meters to get your BMI.

    BMI = weight (kg) ÷ height (m)²

Methodology & Sources

Reviewed and updated April 14, 2026 · Prepared by GetHealthyCalculators Editorial Team

This calculator uses the Quetelet index (BMI = kg/m²), originally described by Adolphe Quetelet in 1832 and adopted by the World Health Organization as a population-level screening tool. Classification cut-points (18.5, 25, 30 kg/m²) were standardized in the 1997 WHO Consultation on Obesity. Accuracy varies by age, sex, ethnicity, and muscle mass — BMI may overestimate adiposity in muscular individuals and underestimate it in older adults. Always consult a qualified healthcare provider for personalized assessment.

References

  • About Adult BMI · Centers for Disease Control and Prevention
  • Obesity: Preventing and Managing the Global Epidemic (WHO Technical Report Series 894) · World Health Organization, 2000
  • Association of all-cause mortality with overweight and obesity using standard body mass index categories: a systematic review and meta-analysis (Flegal KM et al., JAMA 2013;309(1):71–82) · JAMA
  • Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults · NIH National Heart, Lung, and Blood Institute (NHLBI)
  • Recherches sur le poids de l'homme aux différents âges (Quetelet A., 1832) · Nouveaux Mémoires de l'Académie Royale des Sciences et Belles-Lettres de Bruxelles
  • Beyond BMI: The Need for New Guidelines Governing the Assessment of Overweight and Obesity (Nuttall FQ, Nutrition Today 2015;50(3):117–128) · Nutrition Today

How to Interpret Your Results

BMI values are grouped into categories defined by the World Health Organization (WHO). These categories help identify potential weight-related health risks. Keep in mind that BMI is a screening tool and does not directly measure body fat percentage or overall health.

Underweight
0–18.4 — Below healthy weight range. Consult a healthcare provider if concerned.
Healthy Weight
18.5–24.9 — Within the healthy weight range for your height.
Overweight
25–29.9 — Above healthy weight range. Consider lifestyle modifications.
Obese (Class I)
30–34.9 — Increased health risks. Consult a healthcare provider.
Obese (Class II)
35–39.9 — Significant health risks. Medical consultation recommended.
Obese (Class III)
40–100 — Severe health risks. Immediate medical consultation recommended.

Limitations

  • BMI does not distinguish between muscle mass and fat. Athletes or muscular individuals may have a high BMI despite low body fat.
  • BMI does not account for bone density, body composition, fat distribution (visceral vs. subcutaneous), or overall fitness level.
  • BMI categories may not apply equally to children, elderly individuals, pregnant women, or certain ethnic groups. Evidence suggests Asian populations may experience obesity-related health risks at lower BMI thresholds.
  • BMI cannot detect sarcopenic obesity — low muscle mass paired with high fat mass — which is common in older adults.
  • BMI does not assess metabolic health markers such as blood pressure, lipids, or insulin resistance that often drive cardiovascular risk.
  • BMI is a screening tool only and should not be used as a medical diagnosis. Always consult a qualified healthcare provider for personalized assessment.

Frequently Asked Questions

What is BMI and how is it calculated?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in meters squared. It provides a numerical value that corresponds to weight categories established by the World Health Organization.
What is a healthy BMI range?
A BMI between 18.5 and 24.9 is considered a healthy weight range for most adults. However, individual health depends on many factors beyond BMI, including muscle mass, diet, activity level, and family history.
Is BMI accurate for athletes and muscular individuals?
BMI may overestimate body fat in athletes and people with high muscle mass, since it cannot distinguish between muscle and fat. If you are highly active or muscular, consider additional assessments like body fat percentage measurement.
Does BMI apply to children and teenagers?
Standard BMI categories are designed for adults aged 20 and older. For children and teens, BMI is calculated the same way but interpreted using age- and sex-specific percentile charts.
What should I do if my BMI is outside the healthy range?
If your BMI is outside the healthy range, consider consulting a healthcare provider or registered dietitian. They can provide personalized recommendations for diet, exercise, and lifestyle changes based on your individual health profile.
Can you have a normal BMI but an unhealthy body fat percentage?
Yes. BMI does not measure fat directly, so someone can fall in the normal BMI range while still carrying excess body fat or having low muscle mass. That is why body fat percentage and waist-to-hip ratio can add useful context.
Does BMI mean the same thing for men and women?
The BMI equation is the same for men and women, but body composition differs by sex. Women naturally carry a higher percentage of essential fat, so BMI should be interpreted alongside other health markers rather than in isolation.
How often should I check my BMI?
For most adults, measuring BMI every 6–12 months at a routine physical is sufficient. If you are actively working on weight goals, monthly check-ins alongside waist measurements and body composition can give a fuller picture than BMI alone.
How does BMI compare to DXA or other body-composition scans?
DXA (dual-energy X-ray absorptiometry) and bioelectrical impedance directly estimate fat and lean tissue, whereas BMI infers category from height and weight only. DXA is considered the clinical gold standard when precise body fat percentage matters.
Does BMI apply the same way across ethnic groups?
Evidence suggests East and South Asian populations may develop cardiometabolic disease at lower BMIs, so the WHO has proposed lower action thresholds (23 kg/m² overweight, 27.5 kg/m² obesity) for these groups. Discuss culturally appropriate cut-points with your healthcare provider.

Get a more detailed picture of your body composition

Body Fat Calculator

Related Calculators

Body Fat Calculator

Estimate your body fat percentage using the U.S. Navy circumference method.

Calculate

Ideal Weight Calculator

Find your ideal weight range using four clinically recognized formulas.

Calculate

TDEE Calculator

Estimate your Total Daily Energy Expenditure based on activity level.

Calculate

Calorie Calculator

Find your daily calorie goal for weight loss, maintenance, or gain.

Calculate

Body Type Calculator

Determine your somatotype (ectomorph, mesomorph, or endomorph) with training and nutrition guidance.

Calculate

Skinfold Body Fat Calculator

Calculate your body fat percentage using Jackson-Pollock 3-site and 7-site caliper formulas.

Calculate

Child & Teen BMI Percentile Calculator

Calculate BMI percentile for children and teens ages 2-20 using CDC growth charts.

Calculate

Body Surface Area Calculator

Calculate your body surface area using DuBois, Mosteller, and Haycock formulas.

Calculate

Body Roundness Index Calculator

Calculate your Body Roundness Index to assess body shape and health risk from waist and height.

Calculate

More on This Topic

LiftProof · Guide

Body Recomposition: Build Muscle and Lose Fat at the Same Time

Evidence-based strategies for simultaneous muscle gain and fat loss.

Read more

PeptideWise · Research Profile

AOD-9604: The Fat-Loss Peptide

Research profile on AOD-9604 and its effects on fat metabolism.

Read more