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BMI Calculator

Calculate your Body Mass Index (BMI) to check if you're at a healthy weight. Get instant results with health insights.

Sex
cm
kg
Your BMI
22.9kg/m²
Normal
<18.518.5253040+
18.5 – 24.9Healthy Range
57 – 76 kgIdeal Weight
Estimated body fat18.2%

Your BMI is in the healthy range. Keep up balanced eating and regular activity.

BMI is a screening tool, not a diagnosis. It does not account for muscle mass, body composition, age, or ethnicity. Consult a healthcare professional for personalized advice.

What is BMI?

Body Mass Index (BMI) is a simple calculation using your height and weight to estimate body fat and screen for weight categories — underweight, normal, overweight, and obesity. While BMI doesn't measure body fat directly, it correlates with more direct measures for most adults.

How BMI is calculated

BMI comes from a simple ratio of your weight to the square of your height — no special equipment needed. The two formulas below give the same result; use the one that matches your units.

Metric (kg, m)BMI = weight (kg) ÷ height (m)²
US units (lb, in)BMI = 703 × weight (lb) ÷ height (in)²

For example, someone 1.75 m (5′9″) tall weighing 70 kg (154 lb) has a BMI of 70 ÷ 1.75² ≈ 22.9, which falls in the normal range.

BMI Categories

Below 18.5UnderweightMay indicate insufficient weight for your height.
18.5 – 24.9NormalAssociated with the lowest health risk.
25.0 – 29.9OverweightIncreased risk of weight-related conditions.
30.0 and aboveObeseHigher risk of cardiovascular and metabolic disease.

BMI Prime and Ponderal Index

BMI Prime. BMI Prime expresses your BMI as a fraction of the upper healthy limit of 25 — simply BMI ÷ 25. A value below 1.0 means you are at or under the healthy ceiling, while above 1.0 indicates overweight, so you can see how far you are from the normal range at a glance.

Ponderal Index. The Ponderal Index (PI) works like BMI but cubes your height instead of squaring it: PI = weight (kg) ÷ height (m)³. For that reason, it stays more consistent for very tall or very short people, where BMI tends to over- or understate body fat.

Estimated body fat

When you enter your age and sex, we also estimate your body-fat percentage with the Deurenberg equation: body fat % = 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4 (sex is 1 for men and 0 for women). It is only an approximation derived from your BMI — not a measurement — but it adds context that BMI alone cannot, which is why age and sex are requested.

Limitations of BMI

BMI is a quick estimate, not a direct measure of body fat, and it cannot tell muscle from fat. Very muscular people, such as athletes, may score high yet be perfectly healthy, while the figure can understate fat in older adults, who typically carry more of it than younger people at the same BMI. Body-fat distribution also differs between men and women. Treat BMI as one useful signal among several, and pair it with professional advice rather than reading it as a diagnosis.

Frequently Asked Questions

What is a healthy BMI?

A healthy BMI is between 18.5 and 24.9. This range is associated with the lowest health risks for most adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese.

How do I calculate my BMI?

Divide your weight in kilograms by your height in meters squared. In imperial units, multiply your weight in pounds by 703, then divide by your height in inches squared.

Is BMI accurate for athletes?

BMI can overestimate body fat in athletes and muscular people because it doesn't distinguish muscle from fat. Consider measures like body fat percentage alongside BMI.

What BMI is considered obese?

A BMI of 30 or higher is classified as obese, often split into Class 1 (30–34.9), Class 2 (35–39.9), and Class 3 (40 and above).

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