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BMI Calculator — Free Online Tool

Body Mass Index — metric and imperial

Calculate your Body Mass Index (BMI) in metric or imperial. Free BMI calculator with health-range chart.

cm
kg
Your BMI
—
Enter your height and weight
<18.5 Under 18.5–24.9 Normal 25–29.9 Over ≥30 Obese
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Free BMI calculator — metric & imperial, instant result

Toololis BMI Calculator computes Body Mass Index using the WHO standard formula. Enter height and weight in either metric (cm / kg) or imperial (ft·in / lb) — conversions happen automatically. Your BMI, category, and healthy weight range appear live.

BMI formula

  • Metric: BMI = weight(kg) ÷ height(m)²
  • Imperial: BMI = (weight(lb) ÷ height(in)²) × 703

BMI categories (WHO, adult)

  • Underweight: < 18.5
  • Normal: 18.5 – 24.9
  • Overweight: 25 – 29.9
  • Obese Class I: 30 – 34.9
  • Obese Class II: 35 – 39.9
  • Obese Class III: ≥ 40

How to use this tool

  1. 1

    Pick your unit system

    Toggle between Metric (cm/kg) and Imperial (ft/in/lb). Numbers update automatically when you switch.

  2. 2

    Enter height and weight

    Type your height and weight. The BMI is computed live — no need to click a button.

  3. 3

    Read the result

    Your BMI appears with a category label (Underweight, Normal, Overweight, Obese). The gauge shows where you sit on the standard WHO scale.

BMI limitations

  • Muscle mass — High-muscle individuals often exceed "Normal" despite low body fat
  • Age — Older adults lose muscle and bone; same BMI can mean different compositions
  • Body shape — BMI doesn\'t show fat distribution (belly fat is higher risk than hip fat)
  • Ethnicity — Asian populations face health risks at lower BMI thresholds
  • Pregnancy — BMI is not valid during pregnancy

For a more complete picture, pair BMI with waist circumference, body fat percentage, and resting heart rate / fitness level. For health decisions, always consult a qualified healthcare professional.

Frequently Asked Questions

What is BMI?
Body Mass Index — your weight divided by your height squared. Formula: BMI = weight(kg) / height(m)². It's a rough screening tool for weight status at the population level.
What are the BMI categories?
WHO standard: Underweight < 18.5, Normal 18.5–24.9, Overweight 25–29.9, Obese ≥ 30. Obese is further split into Class I (30–34.9), Class II (35–39.9), and Class III (≥ 40).
Is BMI accurate for athletes?
Often not. BMI does not distinguish muscle from fat. A muscular athlete can have a BMI of 27 (Overweight by the chart) while having 10% body fat — physically healthier than most "Normal BMI" individuals. Use waist-to-height ratio or body fat % for athletes.
Is BMI valid for children?
Children and teens use a different BMI calculation that accounts for age and sex (BMI-for-age percentiles). This calculator is for adults 20+ only.
Does BMI differ by ethnicity?
Yes. Research shows people of Asian descent develop health risks at lower BMI thresholds — WHO suggests a cutoff of 23 (rather than 25) for Overweight in Asian populations. This calculator uses standard thresholds; adjust interpretation accordingly.
Should I change my weight based on BMI?
BMI is a starting conversation, not a verdict. Combined with waist circumference, body composition, family history, and fitness level, it becomes useful. For health decisions, consult a clinician rather than acting on BMI alone.
What is ideal weight for my height?
The "healthy range" for your height is any weight that gives a BMI between 18.5 and 24.9. For a 170 cm adult, that's 53.5–72 kg. The calculator shows your healthy range based on your input.

Key Takeaways

  • BMI Calculator is a free, browser-based calculator tool — body mass index — metric and imperial.
  • No signup, no downloads, no file uploads — your data stays on your device.
  • Works on desktop, tablet, and mobile. Install as a PWA for offline access.

How to Use BMI Calculator

  1. Open the tool: Launch BMI Calculator on Toololis — no account or download needed.
  2. Enter your data: Paste text, enter values, or select a file directly in your browser.
  3. Get instant results: Everything is processed locally — results appear immediately.
  4. Copy or download: Save your output or share it. Bookmark for quick access next time.

BMI Calculator — Quick Facts

Price
Free — no limits, no watermarks, no paywalls
Privacy
100% browser-based — no data is sent to any server
Platform
Any modern browser on desktop, tablet, or mobile
Category
Calculator Tools on Toololis
Offline
Works offline after first visit (Progressive Web App)
FeatureDetails
ToolBMI Calculator
CategoryCalculator
Signup RequiredNo
File UploadNone — processed in browser
Mobile SupportFully responsive
CostFree forever

Why Use BMI Calculator?

You should try BMI Calculator for a quick, private way to body mass index — metric and imperial. All processing happens in your browser. Your files and data never leave your device. According to web.dev, client-side processing is the gold standard for privacy.

On the other hand, dedicated APIs or desktop tools suit batch processing better. They also handle server-side automation. For everyday tasks, browser tools offer the best speed, privacy, and convenience.

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100% Privacy. This tool runs entirely in your browser. Your data is never uploaded to any server.