Body composition screening
BMI Calculator
Body mass index compares your weight with your height. It is a quick population-level screening number, useful as one piece of context and not as a verdict on your health.
Your information stays on this device. Nothing you type is sent to a server, saved to an account or added to analytics.
Your results
How to read your BMI category
For adults aged 20 and over, the standard categories are underweight below 18.5, healthy weight from 18.5 to 24.9, overweight from 25.0 to 29.9 and obesity at 30.0 and above. Because the boundaries are fixed, small changes in weight can move you across a line without meaningfully changing anything about your body.
If you want numbers you can act on, energy estimates are more useful than BMI. Start with the BMR calculator for resting energy, or read our guide to tracking progress without letting the scale run your week.
Suggested next calculators
- Run every number in the all-in-one fitness calculator
One set of inputs, every number: BMI, BMR, maintenance, target and macros.
- Open the bmr calculator
Estimate the energy your body uses at complete rest.
- Open the tdee calculator
Estimate the total energy you use across a normal day.
Relevant guides
- How Many Calories Should I Eat Per Day? Calculate, Test and Adjust Your Starting Target
Learn how to estimate your daily calorie target for maintenance, fat loss or weight gain, why a fixed 500-calorie cut does not suit everyone, and how to calibrate your number over 14 days.
- BMR vs TDEE: What’s the Difference, and Which Number Should You Use?
BMR is the energy your body burns at complete rest; TDEE adds all movement on top. Neither number is your calorie intake target — that requires choosing a goal. This guide explains the difference clearly.
- Is BMI Accurate? What It Measures, What It Misses, and What to Check Next
Understand what BMI actually measures, why it is still used in medicine, its key limitations for athletes and diverse populations, and a practical five-layer framework to interpret your result.