Learning how to calculate BMI takes about ten seconds with the right tool. Body Mass Index is a quick screening number that compares your weight to your height, and it is the starting point most doctors and coaches use for a healthy-weight conversation. This guide shows you how to calculate BMI two ways – instantly with our free calculator, or by hand with the formula – and includes a printable BMI chart and tracker you can stick on the fridge.
Last updated: July 24, 2026. Category ranges follow the standard CDC adult BMI guidance.
How to Calculate BMI: Quick Facts
Last updated: July 24, 2026
- Metric formula: weight (kg) divided by height (m) squared.
- Imperial formula: 703 times weight (lb) divided by height (in) squared.
- Healthy range: BMI 18.5 to 24.9 for most adults.
- Fastest way: use our free BMI calculator – enter height and weight, get your number instantly.
- Limitation: BMI does not measure body fat directly and can over-read for very muscular people.
The Fastest Way: Use the Free BMI Calculator
The simplest way to calculate BMI is to let the tool do the math. Open our free BMI Calculator, choose metric or imperial units, enter your height and weight, and press Calculate. It instantly returns your BMI number and the category it falls in, color-coded from underweight to obese. No sign-up, no app, and it works on your phone.
How to Calculate BMI by Hand
If you want to do it yourself, the formula is straightforward. In metric units, divide your weight in kilograms by your height in meters squared. Example: 75 kg divided by (1.78 m x 1.78 m) equals a BMI of about 23.7. In imperial units, multiply your weight in pounds by 703, then divide by your height in inches squared. Example: 165 lb times 703, divided by (70 in x 70 in), equals a BMI of about 23.7 as well.
BMI Categories
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Normal weight |
| 25.0 to 29.9 | Overweight |
| 30.0 and above | Obese |
The printable chart above adds a healthy-weight quick reference for common heights, plus a blank tracker so you can log your BMI over time. Remember that BMI is a screening estimate, not a diagnosis – it is a useful starting point, not the whole picture.
More Free Fitness Tools
- BMI Calculator – your instant Body Mass Index in metric or imperial.
- 1RM Calculator – estimate your one-rep max for any lift.
- All Sports Tools & Calculators
Frequently Asked Questions: Calculating BMI
What is the formula to calculate BMI?
BMI equals weight in kilograms divided by height in meters squared. In imperial units, it is 703 times weight in pounds divided by height in inches squared. Our free BMI calculator does the math for you in either unit system.
What BMI is considered healthy?
For most adults, a BMI between 18.5 and 24.9 is the normal, healthy-weight range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is classified as obese.
Is BMI the same for men and women?
Yes, the standard adult BMI formula and category ranges are the same for men and women. It is calculated for children and teens differently, using age-and-sex percentiles rather than the fixed adult ranges.
