BMI Calculator

Calculate your BMI (Body Mass Index) from height and weight in metric or imperial, with your category and healthy-weight range.

100% Browser-Based • Local Processing
Units
cm
kg

BMI is a screening estimate, not a diagnosis, and it does not tell muscle from fat. It is not designed for children, pregnancy, or highly muscular builds. This is not medical advice.

Normal weight

24.2

Category Normal
Healthy range 53.5–72.0 kg
To that range Already in it
Formula and working

The formula

BMI = weight (kg) ÷ height (m)²

Your numbers

70 ÷ 1.7² = 24.2

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Privacy Focused

🔒 Local Processing. Your numbers never leave your device.

Instant Results

🌐 Fully Client-Side. Runs instantly in your browser.

No Signup

⚡ No accounts. No API keys. Just open and use.

Browser Based

🚀 No installs, no sign-ups, no server round-trip.

Overview

What is a BMI Calculator?

A BMI Calculator works out your Body Mass Index from your height and weight, then shows which category it falls in — underweight, normal, overweight, or obese — and your healthy-weight range. BMI = weight (kg) ÷ height (m)². Enter your figures in metric or imperial and it calculates instantly in your browser.

Body Mass Index (BMI) is a quick, widely used screening number that relates your weight to your height. It's a useful first indicator of whether your weight is in a healthy range for your height — though it's a general estimate, not a full picture of health.

This calculator gives your BMI and category in metric or imperial units, shows the formula, and tells you the healthy-weight range for your height. It runs entirely in your browser, so your details stay private.

Guide

How to calculate your BMI

Step 1: Choose metric or imperial units

Choose metric or imperial units.

Step 2: Enter your height and weight

Enter your height and weight.

Step 3: Read your BMI, its category, and the healthy-weight range for your height

Read your BMI, its category, and the healthy-weight range for your height.

Screens

BMI Calculator in action

BMI Calculator showing Body Mass Index and category in the browser.
BMI + category
BMI result with the healthy-weight range for the height.
Healthy range
Calculating BMI on a phone, no app installed.
Mobile (stacked)
Details

What BMI is — and what it isn't

BMI is calculated as weight in kilograms divided by height in metres squared (kg/m²); in imperial units the equivalent is 703 × weight(lb) ÷ height(in)². For adults, the standard categories are: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30 or above obese. It's popular because it needs only height and weight and gives a fast population-level sense of weight status. But its limits matter and we state them plainly: BMI doesn't distinguish muscle from fat, so very muscular people (athletes) can read as 'overweight' despite low body fat, and it can under-flag people with low muscle. It also doesn't apply the same way to children and teens (who use age-and-sex percentiles), pregnant people, or the elderly, and it ignores where fat is carried, which affects health risk. So treat BMI as a screening estimate and a starting point for conversation, not a diagnosis — for a fuller picture, combine it with body-fat percentage and waist measurement, and consult a healthcare professional. This is not medical advice. Everything computes locally in your browser. See also the Body Fat, Ideal Weight, and BMR calculators.

Support

Frequently Asked Questions

How is BMI calculated?

BMI = weight (kg) ÷ height (m)². For example, 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) = 22.9. In imperial units it's 703 × weight (lb) ÷ height (in)². The calculator does the unit handling and shows the formula, so you get the value and can see how it was worked out.

What are the BMI categories?

For adults: below 18.5 is underweight, 18.5 to 24.9 is normal (healthy) weight, 25 to 29.9 is overweight, and 30 or above is obese. The calculator shows which band your BMI falls in. These ranges are general adult guidelines and don't apply the same way to everyone.

Is BMI accurate for athletes or very muscular people?

Not really. BMI uses only height and weight, so it can't tell muscle from fat. Muscular people often have a high BMI that classes them as 'overweight' despite low body fat. For them, body-fat percentage or other measures give a truer picture, which is why BMI is a screening tool, not a verdict.

Does BMI work for children?

Not with the adult categories. Children and teens are assessed using BMI-for-age percentiles that account for sex and growth, because healthy ranges change as they develop. This calculator uses the adult formula and categories, so for under-18s consult a paediatric BMI percentile chart or a doctor.

What's a healthy BMI range?

A BMI of 18.5 to 24.9 is generally considered the healthy range for adults. The calculator also shows the actual weight range that corresponds to this band for your specific height, so you can see the healthy-weight window in kilograms or pounds rather than just the BMI numbers.

Is BMI a measure of health or just weight?

It's a measure of weight relative to height, not overall health. It doesn't capture body composition, fat distribution, fitness, diet, or medical conditions. A 'normal' BMI doesn't guarantee good health, and a high one isn't always a problem. Use it as one general indicator alongside other measures and professional guidance — it isn't medical advice.

Is it free, and do I need to sign up?

Yes, it's completely free with no account, no trial, and no limit on how many times you use it. It runs entirely in your browser, so there's no sign-in wall — just open the page and calculate.

Is my data private?

Yes. Everything is calculated in your browser — the numbers you enter are never sent to a server, and nothing is stored once you close the tab. That keeps any personal figures (salary, loan, health) on your own device.

Does it work on mobile?

Yes. It runs in your phone's browser with nothing to install, so you can calculate on Android or iOS. The layout adapts to small screens, so entering numbers and reading the result is easy on the go.

Does it work offline?

Once the page has loaded, the calculation runs entirely on your device, so it keeps working without a connection. You only need to be online to open the page the first time — which is also why nothing you enter is uploaded.

Can I copy or share the result?

Yes. You can copy the result to your clipboard with one click, and many results can be shared. Because everything is calculated locally, copying is instant with no upload step.

How accurate is it, and is this professional advice?

The math is accurate for the inputs you give, and the formula is shown so you can verify it. But results are estimates for general use, not professional advice — finance calculators use simplified assumptions and ignore fees and rate changes, and health calculators are general estimates, not medical advice. For important decisions, consult a qualified professional.

Still have questions?

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