BMI Calculator
Body mass index and healthy range.
Calculate your Body Mass Index (BMI) from height and weight. Shows WHO and Asia‑Pacific reference ranges.
See also: BMI Limits: When BMI Misleads and What to Use Instead, Unit Conversion Mistakes: Common Errors and Fixes, Understanding Compound Interest (APR, APY, Compounding Frequency), Loan Repayment Methods: Equal Payment vs. Equal Principal · Unit Converter, Age Calculator, Average Calculator.
When this calculator helps most
Use BMI when you need a quick, comparable screening number from just height and weight — for example before a check-up, when comparing population trends, or when a form asks for BMI. Pair it with waist circumference or clinical advice whenever the result is near a cutoff or you have high muscle mass.
What each input means
- Weight — Total body mass; use consistent units (kg with cm, or lb with inches). (kg or lb)
- Height — Standing height without shoes for best consistency. (cm or ft/in)
Input mistakes to avoid
- •Measure height without shoes and weight with light clothing for consistency.
- •Do not mix units (e.g., kg with inches) — the tool expects coherent metric or imperial pairs.
- •If you are pregnant, postpartum, or have conditions that affect fluid balance, BMI alone may be misleading.
BMI Calculator
Formula
Examples
70 kg, 175 cm
Adult example within normal range.
→ BMI ≈ 22.9 (Normal)
How to read your results
- →BMI maps to broad categories (underweight / normal / overweight / obesity) for screening — not diagnosis.
- →A value near a cutoff should be interpreted with waist circumference, activity, and clinical context.
- →Asia-Pacific references often flag risk at lower BMI than WHO global cutoffs.
- →High BMI with low body fat (athletes) and “normal” BMI with high visceral fat both require expert interpretation.
What this result means
Your BMI value places you in a broad population screening band. It answers “how heavy for how tall” in one number — not “how healthy you are” in a clinical sense.
Common Pitfalls
- ⚠️Treating BMI as a diagnosis rather than a screening metric.
- ⚠️Applying adult BMI categories to children — use percentiles.
Tips
- ✓BMI is a screening metric, not a diagnosis.
- ✓For Asian populations, normal is often below 23.
How to check your results
- ✓Recalculate manually: kg ÷ (m²) or 703 × lb ÷ in² and compare to the first two decimal places.
- ✓If the category surprises you, re-check height/foot-inch entry and unit toggle.
Warnings & Limitations
- ⚠️Consult a healthcare professional for medical decisions.
What this calculator does not tell you
- –Body fat percentage, visceral fat, or where fat is stored.
- –Fitness, strength, blood pressure, blood sugar, or lipid levels.
- –Whether a child is healthy — pediatric BMI uses percentiles, not adult cutoffs.
- –Individual risk of disease; screening categories are statistical, not personal diagnoses.
Frequently Asked Questions
What is BMI and what does it measure?
BMI (Body Mass Index) is a number derived from your weight and height. It is used as a population-level screening indicator for underweight, normal weight, overweight, and obesity. BMI does not directly measure body fat percentage, body composition, fitness level, or metabolic health — it is a proxy measurement, not a diagnostic.
What is the BMI formula?
Metric: BMI = weight (kg) ÷ height² (m²). Example: 70 kg, 1.75 m → BMI = 70 ÷ 3.0625 = 22.9. Imperial: BMI = 703 × weight (lbs) ÷ height² (inches²). Example: 154 lbs, 69 inches → BMI = 703 × 154 ÷ 4761 = 22.7.
What are the WHO BMI categories?
WHO standard categories: Under 18.5 = Underweight | 18.5–24.9 = Normal weight | 25.0–29.9 = Overweight | 30.0–34.9 = Obese Class I | 35.0–39.9 = Obese Class II | 40.0+ = Obese Class III (Severe obesity). These thresholds are based on studies primarily conducted on European populations.
Do Asian populations use different BMI cutoffs?
Yes. Multiple health organizations in Asia recommend adjusted thresholds due to evidence that Asian populations face higher metabolic risks (type 2 diabetes, cardiovascular disease) at lower BMI values. Common Asian-Pacific reference ranges: Under 18.5 = Underweight | 18.5–22.9 = Normal | 23–27.4 = Overweight | 27.5+ = Obese. The World Health Organization has acknowledged these differences and published expert consultation reports on the topic.
Is BMI accurate for athletes and muscular people?
BMI significantly overestimates obesity risk in athletes. Muscle is much denser than fat — a 90 kg rugby player and a 90 kg sedentary person have the same BMI but very different health profiles. For people with high muscle mass, body fat percentage, waist circumference, or DEXA scan data are better indicators of health risk than BMI.
Is BMI accurate for older adults?
BMI can underestimate health risk in older adults, who tend to lose muscle mass (sarcopenia) while fat mass stays the same or increases. An older adult with a "normal" BMI may have high body fat percentage due to low muscle mass. Healthcare providers often use BMI alongside other assessments (grip strength, waist circumference) in older patients.
What is a healthy BMI for children?
Adult BMI categories do not apply to children and teens. For those under 18, BMI is plotted on age- and sex-specific growth charts as a percentile, not compared to fixed thresholds. A pediatrician or school health service should interpret children's BMI results.
What should I do if my BMI is outside the normal range?
A BMI result outside the normal range is a reason to consult a healthcare professional, not a diagnosis. A doctor or dietitian can put your BMI in context alongside other health indicators — blood pressure, fasting glucose, lipid panel, waist circumference, and activity level — to give a meaningful health picture.
Sources & References
Editorial & review note
Bands follow common screening references; Asia–Pacific cutoffs are highlighted where users might otherwise apply the wrong chart. Updates track public guidance changes—clinical decisions still belong with a provider.
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Disclaimer: BMI does not account for muscle mass, bone density, age, sex, ethnicity, or fat distribution. For medical decisions, consult a professional.