BMI Calculator
Body Mass Index is a quick screening tool that relates your weight to your height. Enter your measurements to find your BMI and what it means.
Last updated: August 2026 · Written and verified by Akash Pandey
Calculate your BMI
BMI
This runs the same calculation engine as the main scientific calculator, entirely in your browser. Nothing you type is sent anywhere.
What is BMI?
Body Mass Index (BMI) is a number calculated from your weight and height. It provides a simple way to classify whether your weight is in a healthy range for your height.
BMI = weight (kg) ÷ height² (m²)
BMI categories
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity (Class I) |
| 35.0 – 39.9 | Obesity (Class II) |
| 40.0 and above | Obesity (Class III) |
Worked example
Calculate BMI for a person 70 kg and 175 cm tall
70 ÷ (1.75)²
- Convert height to metres:
175 cm = 1.75 m. - Square the height:
1.75² = 3.0625. - Divide weight by height squared:
70 ÷ 3.0625 ≈ 22.86. - This falls in the "Normal weight" category (18.5–24.9).
= 22.86
- Convert height to metres:
Limitations of BMI
BMI is a useful screening tool, but it has limitations. It does not distinguish between muscle and fat, so muscular athletes may be classified as overweight despite having low body fat. It also does not account for fat distribution, bone density, or age.
Frequently Asked Questions
Is BMI accurate?
BMI is a useful screening tool for most people, but it does not account for muscle mass, bone density, or fat distribution. Athletes and muscular individuals may have a high BMI despite having low body fat.
What is a healthy BMI?
A BMI between 18.5 and 24.9 is generally considered normal weight. However, BMI should be considered alongside other factors like waist circumference and overall health.
Does BMI differ for men and women?
The BMI calculation is the same for both sexes. However, women tend to have more body fat than men at the same BMI, so the healthy range may differ slightly.
What is a good BMI for my age?
The healthy BMI range (18.5–24.9) is the same for adults of all ages. However, older adults may have slightly higher BMI without increased health risk due to changes in body composition.
How do I calculate BMI for a child?
Children and teens use age- and sex-specific BMI percentile charts rather than the standard adult categories. A paediatrician can interpret the percentile correctly.
What is the difference between BMI and body fat percentage?
BMI is a ratio of weight to height. Body fat percentage measures actual fat mass. An athlete may have a high BMI due to muscle but a low body fat percentage.
Does BMI change with height?
Yes. BMI is weight divided by height squared, so taller people need more weight to have the same BMI as shorter people. The formula already accounts for this.
Is BMI used worldwide?
Yes. BMI is the most widely used screening tool for weight categories. However, different populations (e.g. Asian and European) may have different healthy BMI thresholds.