BMI Calculator — Free Online Tool

Check your Body Mass Index with metric or imperial units. · No signup · Works on mobile

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100% private: your data is processed in your browser. Nothing is uploaded to our servers.

How to use the bmi calculator

  1. 1

    Choose metric (kg/cm) or imperial (lb/ft-in) units.

  2. 2

    Enter your height and current weight.

  3. 3

    See your BMI score, weight category, and healthy weight range instantly.

What does this tool do?

This free BMI calculator gives your Body Mass Index instantly from your height and weight, in metric (kg/cm) or imperial (lbs/ft-in) units. It shows your BMI value, your WHO weight category — underweight, normal, overweight, or obese — and the healthy weight range for your height.

How does the bmi calculator work?

BMI = weight (kg) ÷ height (m)². For imperial units the formula is 703 × weight (lb) ÷ height (in)². The WHO classifies BMI under 18.5 as underweight, 18.5–24.9 as normal, 25–29.9 as overweight, and 30+ as obese.

Frequently Asked Questions

What is a healthy BMI range?

The World Health Organization defines a normal BMI as 18.5–24.9. For a person 170 cm tall, that corresponds to a weight of roughly 53.5–72 kg. Some Asian-population guidelines use a lower overweight threshold of 23 due to different cardiometabolic risk profiles.

Is BMI accurate for athletes and bodybuilders?

Not always. BMI cannot distinguish muscle from fat, so muscular athletes often register as "overweight" despite low body fat — many professional rugby players have BMIs above 27. For muscular builds, waist-to-height ratio or a body fat measurement gives a truer health picture.

Is the BMI calculator really free?

Yes — 100% free with no hidden charges, trial limits, or premium tiers for core features. You don't need to create an account or enter an email address. The site is supported by non-intrusive display ads, which keeps every tool free for everyone.

Is my data private when using the BMI calculator?

Completely. The BMI calculator runs entirely in your browser using JavaScript — nothing you type or upload is sent to our servers. When you close the tab, your data is gone. This makes it safe for confidential documents, financial figures, and personal information.

Does the BMI calculator work on mobile phones?

Yes. The BMI calculator is built mobile-first and works on any phone or tablet with a modern browser — iPhone (Safari), Android (Chrome), and everything in between. The layout adapts to small screens, so buttons and inputs stay easy to tap on a 375px-wide display.

Do I need to install anything to use the BMI calculator?

No. The BMI calculator works directly in your web browser — no downloads, no extensions, no signup. Just open the page, use the tool, and get your result instantly. It works on Windows, macOS, Linux, ChromeOS, iOS, and Android.