Health & fitness · Body Metrics
BMI Calculator
Calculate your Body Mass Index (BMI) instantly in metric or imperial units. See your weight category and healthy weight range based on WHO guidelines.
How it works
BMI (Body Mass Index) is a measure of body fat based on height and weight. It is used to screen for weight categories that may lead to health problems. A BMI between 18.5 and 24.9 is considered healthy for most adults.
Formula
BMI = weight (kg) / height² (m)
- weight
- Body weight in kilograms
- height
- Height in metres
Step by step
- 1Convert weight to kilograms and height to metres if using imperial units.
- 2Square the height in metres.
- 3Divide the weight by the squared height to get BMI.
- 4Compare the result to WHO categories: Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese (≥30).
Examples
Adult male — metric
70 ÷ (1.75²) = 70 ÷ 3.0625 ≈ 22.9 — within the healthy range.
Inputs
- units:
- metric
- weight_kg:
- 70
- height_cm:
- 175
Result
- bmi:
- 22.9
- category:
- Normal weight
Adult female — imperial
140 lbs ≈ 63.5 kg, 5′5″ = 165.1 cm = 1.651 m; 63.5 ÷ 1.651² ≈ 23.3.
Inputs
- units:
- imperial
- weight_lbs:
- 140
- height_ft:
- 5
- height_in:
- 5
Result
- bmi:
- 23.3
- category:
- Normal weight
Frequently asked questions
What is a healthy BMI?▾
For adults, the WHO considers a BMI of 18.5–24.9 as normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese.
Is BMI accurate for athletes?▾
BMI doesn't distinguish between muscle and fat, so athletes with high muscle mass may have a high BMI while actually having low body fat. Use other measures such as body fat percentage for a fuller picture.