BMI Calculator — Metric & Imperial
Calculate your BMI free using kg and cm or lbs and ft. Get your BMI category, healthy weight range and personalized health tips — no sign-up, works on mobile, completely private.
Last updated: June 2026
Your BMI
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- Healthy weight range
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- Health risk
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Medical Disclaimer: This tool provides general health information for educational purposes only. Always consult a qualified healthcare professional for medical advice, diagnosis, or treatment.
Guide What is BMI? Complete Guide to Body Mass Index Read guide →Why use CrispToolHub?
| Feature | CrispToolHub | calculator.net | NHS BMI |
|---|---|---|---|
| Free | ✅ Always | ✅ Free | ✅ Free |
| Privacy | 🔒 Local | ☁️ Online | ☁️ Online |
| Healthy range + scale | ✅ Full | ⚠️ Basic | ⚠️ Basic |
| Dark mode | ✅ Yes | ❌ No | ❌ No |
About this tool
Understanding your BMI
Body Mass Index (BMI) is the most widely used screening figure for weight relative to height. This BMI calculator takes your weight and height — in metric or imperial units — and returns your BMI to one decimal place, the category it falls into, the healthy weight range for your height, and a colour-coded scale that marks where you sit. It's the quickest way to get a sense of whether your weight is in a healthy range for your build.
The categories follow the standard adult thresholds: under 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or above is obese. Seeing your number on the scale — and the weight range that would put you in the healthy band — turns an abstract figure into something you can act on, whether your goal is to gain, maintain or lose.
BMI's great strength is its simplicity, but that's also its limitation. Because it uses only height and weight, it can't tell muscle from fat or show where fat is stored. A muscular athlete may read as "overweight" while carrying very little fat, and two people with the same BMI can have very different body compositions. That's why it's best treated as a starting point and paired with measures like body fat percentage and waist size, which the related tools cover.
This calculator is for general education only and is not a diagnosis — your health depends on far more than a single number, and you should discuss any concerns with a qualified healthcare professional. Everything is computed in your browser, so your details stay private. Enter your weight and height above to see your BMI, then explore the ideal weight and BMR calculators to build a fuller picture.
How it works
Three quick steps — no account, nothing uploaded to a server.
Choose your units
Switch between metric and imperial.
Enter weight and height
Type your measurements, age and gender are optional.
Read your result
BMI, category, healthy range and scale appear instantly.
General health information related to this tool is available from the US CDC BMI resources. Last checked July 2026.
FAQ
Frequently asked questions
How is BMI calculated?
Body Mass Index is your weight in kilograms divided by the square of your height in metres (kg/m²). In imperial units it's weight in pounds × 703, divided by height in inches squared. This calculator does the conversion for you whichever units you enter, and shows your BMI to one decimal place along with the category it falls into.
What is a healthy BMI range?
For adults, a BMI below 18.5 is classed as underweight, 18.5 to 24.9 as normal (healthy) weight, 25 to 29.9 as overweight, and 30 or above as obese. The 'normal' band is associated with the lowest risk for most people, but BMI is a population guideline, not a personal diagnosis.
What are the limitations of BMI?
BMI uses only height and weight, so it can't distinguish muscle from fat or account for where fat is stored. Very muscular people (such as athletes) may register as overweight despite low body fat, while others may have a 'normal' BMI but high body fat. Treat it as a quick screening number and pair it with measures like body fat percentage and waist circumference.
Is BMI accurate for everyone?
BMI is a useful general indicator for most adults but is less reliable for athletes, the elderly, pregnant women, and people of certain ethnic backgrounds for whom health-risk thresholds differ. Children and teenagers use age- and sex-specific BMI percentiles instead. Always interpret your result with a healthcare professional.
Is my data private?
Yes. The BMI calculation runs entirely in your browser — your weight, height and other details are never uploaded, stored or shared. Nothing leaves your device.
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