BMI Calculator

⚡ Instant 📏 Metric & US 🌍 WHO / 🌏 Asian 🧮 Body fat % & WHtR 🔥 BMR & TDEE

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Understanding your BMI

BMI (Body Mass Index) = weight (kg) ÷ height (m)2. It's a quick screen-not a diagnosis. Muscular people may read "high" despite low body fat, while some with "normal" BMI may still have central obesity.

Your BMI position on the scale above adjusts in real time.
Under Normal Over Obese

References: WHO, Asian BMI cut-offs.

BMI categories and healthy weight range explainer
Visual explainer: BMI categories & healthy weight range.

Frequently Asked Questions

What is a healthy BMI?
Using WHO adult cut-offs: 18.5–24.9 is normal. For many Asian populations, 18.5–22.9 is used. BMI Prime below 1.0 indicates healthy weight; above 1.0 indicates overweight risk.
Is BMI accurate for athletes or bodybuilders?
BMI does not distinguish fat from muscle. Athletes with high muscle mass may register as "overweight" despite having low body fat. Use waist-to-height ratio (WHtR) and body fat % for better context.
Does this work for children?
No. Children require age- and sex-specific percentiles, which this adult calculator does not provide. Consult a pediatrician for child BMI interpretation.
What is BMI Prime and why does it matter?
BMI Prime = BMI ÷ 25. It's a simple ratio where values below 1.0 are below the overweight threshold and above 1.0 are above it. It helps quickly gauge how far you are from the healthy upper limit.
What is WHtR (Waist-to-Height Ratio)?
WHtR = waist circumference ÷ height. Aim for <0.5; 0.50–0.59 means increased risk; ≥0.60 means high risk. It's a simple screen for abdominal obesity, which is a key driver of metabolic disease.
How do I measure my waist correctly?
Measure at the narrowest point of your torso (usually near the navel), or at the midpoint between your lowest rib and hip bone. Keep the tape snug but not tight, and breathe out normally.
What is the BMI formula?
Metric: BMI = weight (kg) ÷ height² (m²). US: BMI = (weight (lb) ÷ height² (in²)) × 703. For example, a 70 kg person at 1.70 m has BMI = 70 ÷ 2.89 = 24.2.
How do I calculate BMI manually?
Take your weight in kg and your height in meters. Square the height, then divide the weight by that number. For imperial: multiply your weight in pounds by 703 and divide by your height in inches squared.

How to Use This BMI Calculator

  1. Select your unit system — Metric (cm/kg) for international, or US/UK (ft/in, lb).
  2. Enter height and weight — for US units, type feet and inches separately.
  3. Choose WHO or Asian cut-offs — WHO uses 18.5–24.9 as normal range; Asian uses 18.5–22.9.
  4. Optionally enter age, sex, and waist — this enables body fat estimation and WHtR calculation.
  5. Click Calculate — your BMI, healthy weight range, BMI Prime, body fat %, WHtR, BMR, and TDEE appear instantly in the results panel.

💡 Tip: Use the Calorie Planner to set a target BMI and see suggested daily calories for your goal.

✅ Do's and ❌ Don'ts for BMI & Weight Management

✅ Do's

  • ✅ Do measure your waist alongside BMI for a complete risk picture.
  • ✅ Do use Asian cut-offs if you're of South Asian, East Asian, or Southeast Asian descent.
  • ✅ Do recalculate BMI as your weight changes over time.
  • ✅ Do combine BMI with other metrics (body fat %, WHtR, blood pressure).
  • ✅ Do consult a doctor if your BMI is consistently above 25 or below 18.5.
  • ✅ Do focus on sustainable habits rather than rapid weight loss.

❌ Don'ts

  • ❌ Don't rely on BMI alone to assess health — it can't measure body composition.
  • ❌ Don't use this calculator for children or pregnant women — different standards apply.
  • ❌ Don't panic about small daily weight fluctuations — measure weekly under the same conditions.
  • ❌ Don't assume a "normal" BMI means you're healthy — fitness and blood markers matter too.
  • ❌ Don't crash diet to lower BMI — it often leads to muscle loss and rebound weight gain.
  • ❌ Don't ignore abdominal fat — a normal BMI with high WHtR still carries health risks.
📐 How BMI is Calculated

Metric formula: BMI = weight (kg) ÷ height² (m²)

US formula: BMI = (weight in lb ÷ height in inches²) × 703

WHO BMI Categories

Underweight
<18.5
Normal
18.5 – 24.9
Overweight
25 – 29.9
Obese
≥ 30

Asian BMI Categories (WHO SEAR/WPR)

Underweight
<18.5
Normal
18.5 – 22.9
Overweight
23 – 24.9
Obese
≥ 25

Worked Example

If you weigh 70 kg and are 170 cm tall:
BMI = 70 ÷ (1.70)² = 70 ÷ 2.89 = 24.2 → Normal range (WHO)

Also try: BMR Calculator · Calorie Calculator · Ideal Weight

Quick explainer 🎥

Frequently Asked Questions

Is this tool free to use?

Yes. All UpTools calculators are completely free, with no sign-ups required.

Is my data private?

Yes. All calculations run locally in your browser. Nothing is uploaded to any server.

Does it work on mobile?

Yes. All tools are mobile-responsive and work on any device — phone, tablet, or desktop.

Can I use this offline?

Most tools work offline after the initial page load. No internet needed for calculations.

📐 How This Tool Works

This tool computes results entirely in your browser using JavaScript. No data is sent to any server, ensuring your privacy.

Results update instantly as you type — no waiting for server responses.

Also try: Calculator · Converter · Generator