Is BMI accurate for everyone?

It’s a population screen, not a diagnosis. Very muscular people and some ethnic groups may need different thresholds.

What formula does the BMI Calculator use?

It calculates using BMI = weight(kg) / height(m)². The guide above walks through what each part means with a worked example.

How accurate is the BMI Calculator?

It uses established, widely-accepted formulas and gives a reliable estimate for the values you enter. Everyone's body is different, so use the result as a helpful guide — not a medical diagnosis.

Is the BMI Calculator a substitute for medical advice?

No. It's an educational estimate. For guidance tailored to you, always consult a qualified healthcare professional before making changes.

Is this calculator free to use?

Yes — every GKCalculators calculator is 100% free with no sign-up required. Create a free account only if you want to save your calculation history across devices.

All calculations run instantly in your browser. Nothing is sent anywhere unless you tap ‘Explain my results’ (AI) or ‘Save’ while signed in.

Can I share my result?

Yes. Tap Share and we copy a link with your exact inputs baked in, so anyone who opens it sees the same result.

BMI Calculator

Health #1

Body Mass Index with WHO categories and your healthy weight range.

Compare

Height (cm)

Weight (kg)

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Your BMI

23.5

Normal

Healthy weight range for your height: 56.7 kg – 76.3 kg

Where you fall

UnderweightNormalOverweightObese

AI Breakdown & Smart Takeaway

Plain-English insight on your numbers

Get a personalized explanation of what these results mean — and how to improve them.

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How the BMI Calculator works

This BMI calculator computes your Body Mass Index from your height and weight, instantly maps your result to the official WHO classification categories, and displays the exact weight range considered healthy for your height — making it essential for anyone tracking their fitness, managing their weight, or discussing health goals with a clinician.

BMI is a quick screen that relates weight to height. We classify it using WHO categories and show your healthy weight range.

It doesn’t distinguish muscle from fat, so athletes can read ‘overweight’ despite being lean — pair it with our Body Fat calculator.

Formula

BMI = weight(kg) / height(m)²

Pro tips

Track BMI over time rather than obsessing over a single reading.

Key terms

Body Mass Index (BMI): — A numerical ratio of weight to height squared (kg/m²) used as a population-level screening indicator of whether a person's body weight falls within a healthy range.
WHO Classification: — The World Health Organization's standardized system that divides BMI scores into labeled categories — Underweight, Normal weight, Overweight, and three classes of Obesity — to assess weight-related health risk.
Healthy Weight Range: — The span of body weights, specific to an individual's height, that corresponds to a BMI between 18.5 and 24.9, representing the lowest statistical risk of weight-related disease.
Obese: — A clinical term for a BMI of 30 or above, indicating excess body weight that statistically raises the risk of conditions such as type 2 diabetes, cardiovascular disease, and certain cancers.
Normal-Weight Obesity: — A condition in which BMI falls within the Normal range but body fat percentage is elevated due to low muscle mass, illustrating a key limitation of BMI as a standalone diagnostic.
Adjusted BMI Thresholds: — Lower BMI cutoff points (Overweight ≥23, Obese ≥27.5) recommended for adults of Asian descent, reflecting greater cardiometabolic risk at lower body weights in these populations.