BMI Calculator
This BMI calculator takes your height and weight and returns your body mass index score alongside the standard weight category it falls in. BMI is a screening number, not a diagnosis. Enter your measurements to see where you land on the clinical scale.
Your BMI score and what the number actually means.
Unit system
BMI
24.2
NormalBMI Prime
0.97
Below upper normal boundary
Healthy weight range
53.5 kg – 72 kg
For your height (BMI 18.5–24.9)
Distance to boundaries
2.2 kg below overweight
WHO Classification Scale
| Category | BMI Range |
|---|---|
| Underweight | < 18.5 |
| Normal | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese Class I | 30.0 – 34.9 |
| Obese Class II | 35.0 – 39.9 |
| Obese Class III | ≥ 40.0 |
BMI is a population-level screening tool and is not validated for children under 20 or adults with high muscle mass. For a more complete picture, consider using a body fat calculator. This is not medical advice.
How this tool works
Body Mass Index divides your weight in kilograms by the square of your height in metres. For imperial units the formula is (weight in pounds / height in inches squared) × 703. The result is classified against six WHO categories: Underweight (below 18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese Class I (30–34.9), Obese Class II (35–39.9), and Obese Class III (40+). The tool also derives a healthy weight range for your height by solving for the weights that produce BMI 18.5 and 24.9, and shows how far your current weight sits from each category boundary. BMI Prime is the ratio of your BMI to the upper normal boundary (24.9); a value below 1.0 means you are in the normal or underweight range.
Worked example
A person weighing 70 kg at 175 cm has BMI = 70 / 1.75² = 22.9 (Normal). Their healthy weight range is 56.7–76.3 kg. They are 13.3 kg above underweight and 5.6 kg below overweight. BMI Prime is 22.9 / 24.9 = 0.92.
Frequently asked questions
What is a healthy BMI?
The World Health Organization defines a healthy BMI as 18.5 to 24.9 for adults. BMI is a population-level screening tool, not a diagnostic measure; muscle mass, age, sex, and ethnicity all affect how the number should be interpreted.
Is BMI accurate for athletes?
BMI overestimates body fat in muscular individuals because muscle is denser than fat. A lean athlete may register as overweight on BMI while having very low body fat. Use body fat percentage tools for a more accurate picture.
Does BMI differ by age or sex?
The BMI formula is the same for all adults, but healthy ranges may differ. Children and teens use age- and sex-specific growth chart percentiles rather than adult BMI cutoffs.
Can BMI predict health risks?
At the population level, high BMI correlates with increased risk of type 2 diabetes, cardiovascular disease, and hypertension. For individuals, waist circumference and body fat percentage add important context that BMI alone cannot provide.