How to Use a Body Mass Index Calculator
- Select your Region (sets units & category cut-offs).
- Enter height and weight (stones & pounds supported).
- (Optional) Add age for tailored notes.
- Tap Calculate BMI to see your BMI, category, healthy range and BMI Prime.
- Use the Converter tab to switch kg↔lb↔stone or cm↔ft/in, and to get target weight for a chosen BMI.
Features (scannable bullets)
- Metric, imperial and stones/ft/in inputs
- Region presets: UK, USA, EU, Asia (WHO Asia)
- BMI category with standard WHO or Asian cut-offs
- Healthy weight ranges (WHO 18.5–24.9; Asian 18.5–22.9)
- BMI Prime (BMI ÷ 25) for at-a-glance risk banding
- Converters + target weight at a chosen BMI
- Age note: guidance if under 18 or 65+
- Mobile-first, accessible, client-side only
Your BMI result explained
- BMI value & category: See where you sit on the scale.
- Healthy weight range: For your height under WHO standards, plus an Asian “normal” range.
- BMI Prime: 1.00 equals BMI 25 (the threshold for overweight in WHO). Values above 1.00 indicate higher BMI relative to that threshold.
- Target weight: Enter a BMI (e.g., 22) in the Converter to get the corresponding weight.
What is BMI?
Body Mass Index (BMI) compares weight to height to screen for weight-related risk.
- Metric: BMI = weight (kg) ÷ height² (m²)
- Imperial: BMI = (weight (lb) × 703) ÷ height² (in²)
BMI is a screening tool, not a diagnosis. It doesn’t directly measure body fat.
BMI categories (country/region aware)
- WHO (most countries, incl. UK/US/EU):
Underweight <18.5 • Normal 18.5–24.9 • Overweight 25–29.9 • Obese ≥30 - WHO Asia (used in some countries and UK guidance for certain ethnic groups):
Underweight <18.5 • Normal 18.5–22.9 • Overweight 23–24.9 • Obese ≥25
When BMI may mislead
BMI can misclassify very muscular athletes, some older adults, and pregnant individuals. For under-18s, use BMI-for-age percentiles (growth charts); speak to a GP/clinician for personal advice.
FAQs
Q1:Do you support stones and feet/inches?
Yes—select UK units or use the Region preset.
Q2:Is my data saved?
No. It’s calculated locally in your browser.
Q3:What’s BMI Prime?
Your BMI relative to 25 (1.00 = BMI 25).
Q4:Which categories does the tool use?
WHO by default, or WHO Asia if you choose the Asia region or toggle Asian cut-offs in Settings.
Q5:Can I get a target weight?
Yes—enter height and a target BMI in the Converter.
