BMI Calculator
Body mass index from your weight and height, with the standard weight category.
Quick answer
- BMI compares your weight with your height: 18.5–24.9 is the normal-weight category for adults, below 18.5 is underweight, 25–29.9 is overweight and 30 or above is obese.
- The healthy weight range shows the weights that give a BMI of exactly 18.5 and exactly 24.9 at your height — in the same weight unit you selected (kilograms in metric mode, pounds in imperial mode).
- BMI is a screening estimate, not a diagnosis: it cannot distinguish muscle from fat, so use the category as a starting point, not a verdict.
- Worked example — Body mass index (BMI): 22.9 (full example below).
BMI Calculator
| Body mass index (BMI) | 22.9 |
| Weight category | Normal weight (18.5–24.9) |
| Healthy weight — low (BMI 18.5), in the weight unit you selected (kg or lb) | 56.7 |
| Healthy weight — high (BMI 24.9), in the weight unit you selected (kg or lb) | 76.3 |
A person weighing 70 kg at 175 cm has a BMI of 22.9 — inside the normal weight range of 18.5–24.9.
Body mass index (BMI) is a screening measure that compares your weight with your height: BMI = weight (kg) ÷ height (m)². It was popularised by the World Health Organization as a quick way to classify adults as underweight, normal weight, overweight or obese.
BMI is an estimate for population screening, not a diagnosis — it does not distinguish muscle from fat, so athletes can score high while being lean. Treat the result as a starting point for a conversation with a clinician, not medical advice.
The formula
Worked example
A person weighing 70 kg at 175 cm has a BMI of 22.9 — inside the normal weight range of 18.5–24.9.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
BMI categories for adults
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5–24.9 |
| Overweight | 25–29.9 |
| Obesity | 30 or above |
Standard WHO/CDC adult categories — the same cut-offs this calculator applies. Children and teens are assessed with age- and sex-specific percentiles instead.
Frequently asked questions
What is a healthy BMI range?
For most adults, 18.5–24.9 is classified as normal weight, below 18.5 is underweight, 25–29.9 is overweight and 30 or above is obese. These cut-offs come from WHO guidance.
Why can BMI be misleading?
BMI ignores body composition and fat distribution. A muscular athlete may be classed overweight, and an older adult with low muscle mass may be classed normal despite high body fat. Waist circumference and body-fat percentage give a fuller picture.
Is BMI used for children?
Not directly — children and teens are assessed with age- and sex-specific BMI percentiles, because healthy body fat changes as they grow. This calculator uses the adult categories.
Category: Health & Fitness calculators
Sources & methodology
Healthy weight range: the low value is the weight that gives a BMI of exactly 18.5 at your height and the high value is the weight that gives exactly 24.9. In metric mode the range is calculated as 18.5 × height (m)² and 24.9 × height (m)² and is shown in kilograms; in imperial mode it is calculated by inverting the 703 formula (weight = BMI × height (in)² ÷ 703) and is shown in pounds. Either way, the range is expressed in the weight unit you selected, matching the weight you entered.
Content last reviewed by CalcHub Editorial.
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