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BMI Calculator

BMI Calculator — get the answer instantly in your browser, free and private.

Metric (kg, cm)Standard (lb, ft/in)
Under 18.5 · Normal 18.5–24.9 · Over 25–29.9 · Obese 30+
Choose metric or standard (imperial) units, enter your weight and height, and your Body Mass Index is calculated instantly along with the weight category. BMI is a quick screening figure — it does not distinguish muscle from fat, so treat it as a guide. Calculated in your browser; nothing is uploaded.

About BMI

This BMI calculator works out your Body Mass Index in either metric (kilograms and centimetres) or standard/imperial (pounds, feet and inches) units, and shows your weight category. BMI is a quick screening measure of whether your weight is in a healthy range for your height. It runs in your browser; nothing is uploaded.

How BMI works

How to use it

  1. Choose Metric or Standard (imperial) units.
  2. Enter your weight and height.
  3. Read your BMI and weight category.

The formula

Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lb) ÷ height (in)². The 703 factor converts pounds-and-inches into the same scale as the metric formula.

Worked example

Metric: 70 kg, 175 cm (1.75 m): 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 → Normal weight.
Imperial: 154 lb, 5 ft 9 in (69 in): 703 × 154 ÷ (69 × 69) = 108,262 ÷ 4,761 = 22.7 → Normal weight.

BMI categories

Under 18.5 = underweight, 18.5–24.9 = normal, 25–29.9 = overweight, 30 and over = obese. BMI is a guide only — it does not account for muscle, bone density, age or sex, so athletes and others may sit outside the "normal" band while being healthy.

Examples

InputBMI
70 kg, 175 cm22.9 (Normal)
90 kg, 180 cm27.8 (Overweight)
55 kg, 170 cm19.0 (Normal)

Common uses

  • Calculate BMI in metric units
  • Calculate BMI in imperial/standard units
  • Check your weight category
  • Track BMI over time
  • Screen weight against height
  • Use kg and cm or lb and ft/in
  • Get a quick health indicator
  • Compare BMI to the healthy range

Frequently asked questions

How is BMI calculated?
Metric: kg ÷ m². Imperial: 703 × lb ÷ in². The tool does both.
Does it support metric and imperial?
Yes — switch between Metric (kg, cm) and Standard (lb, ft/in).
What is a healthy BMI?
18.5 to 24.9 is the normal range.
What are the BMI categories?
Under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese.
Is BMI accurate for everyone?
No — it ignores muscle, age and sex, so use it as a guide, not a diagnosis.
Is my data uploaded?
No — it calculates in your browser.
Is it free?
Yes — completely free with no sign-up.