---
title: BMI Calculator (and Why It Misses Muscle)
url: https://progresslens.app/tools/bmi-calculator/
language: en
updated: 2026-11-13
---

# BMI calculator

BMI is weight divided by height squared. It’s quick, but it can’t tell muscle from fat, so add your waist for a better picture.

Short answer

BMI = weight (kg) ÷ height (m)². For adults, 18.5–24.9 is a healthy weight, 25–29.9 overweight and 30 or more obesity (WHO). BMI can’t tell muscle from fat, so check your waist-to-height ratio too.

Calculated in your browser. Nothing you enter is sent anywhere.

## BMI categories (WHO, adults)

| BMI | Category |
| Under 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25–29.9 | Overweight |
| 30–34.9 | Obesity class I |
| 35–39.9 | Obesity class II |
| 40 or more | Obesity class III |

Some health bodies use lower cut-offs for people of South Asian, Chinese, other Asian, Black African and African-Caribbean backgrounds (UK NICE: 23 for overweight, 27.5 for obesity).

## BMI vs body fat

A muscular 90 kg lifter at 180 cm has a BMI of 27.8, “overweight”, while being lean. And someone with a “healthy” BMI can carry a lot of body fat with little muscle (often called skinny fat). Waist-to-height ratio and body fat say more. Try the [body fat estimator](https://progresslens.app/tools/body-fat-estimator/) or the [waist-to-height ratio calculator](https://progresslens.app/tools/waist-to-height-ratio-calculator/).

## See how far you’ve come.

Take a check-in, tap AI Analyze and get your Progress Report: body-fat range, what changed, fat or muscle, and whether to cut or bulk. On iPhone, iPad and Android, with no account. Your photos stay on your phone.

FAQ

## Frequently asked questions

**What is a healthy BMI?**

18.5 to 24.9 for most adults, by WHO definitions. Your waist and body fat give useful context.

**Is BMI accurate for muscular people?**

No. BMI counts muscle as weight, so lifters often land in “overweight” while lean.

**What’s better than BMI?**

Waist-to-height ratio (keep your waist under half your height) and body fat percentage both track health risk and body composition better.

## More free tools

[Body fat estimatorYour look plus a tape measure, no upload.Open →](https://progresslens.app/tools/body-fat-estimator/)[Bulk or cut calculatorCut, lean bulk or recomp, with a weekly rate.Open →](https://progresslens.app/tools/bulk-or-cut-calculator/)[TDEE calculatorMaintenance calories, and to cut or bulk.Open →](https://progresslens.app/tools/tdee-calculator/)[Macro calculatorProtein, carbs and fat for your goal.Open →](https://progresslens.app/tools/macro-calculator/)[GLP-1 weight loss calculatorOzempic and Mounjaro trial averages for you.Open →](https://progresslens.app/tools/glp-1-weight-loss-calculator/)[Protein calculatorGrams a day for muscle, fat loss or GLP-1.Open →](https://progresslens.app/tools/protein-calculator/)

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ProgressLens is an AI progress photo app for iPhone, iPad and Android that turns your check-in photos and tape measurements into a Progress Report: your body-fat range, what changed, whether you are losing fat or muscle, and whether to cut, lean bulk, recomp or maintain.
App Store: https://apps.apple.com/app/progresslens/id6806300575
Google Play: https://play.google.com/store/apps/details?id=app.progresslens