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BMI Calculator

Body Mass Index from weight and height.

Reviewed by The QuickCalc Editorial Team · Last updated · About our methodology

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Result

BMI
24.5
Category: Healthy weight

Inputs & results at a glance

Updates live as you change the form above.

ItemTypeValue
WeightInput75 kg
HeightInput175 cm
BMIResult24.5
CategoryResultHealthy weight

About this calculator

Body Mass Index (BMI) is a widely used screening measure that estimates whether an adult's weight is in a healthy range for their height. The calculator uses the standard formula BMI = weight (kg) ÷ height (m)², so a person weighing 75 kg standing 1.75 m tall has a BMI of 24.5.

The World Health Organization categorises BMI as follows: below 18.5 is underweight; 18.5–24.9 is a healthy weight; 25–29.9 is overweight; 30 and above is obese, with sub-categories inside the obese range for clinical use. These cutoffs are population averages and don't apply equally to all body types.

BMI is a screening tool, not a diagnosis. It doesn't distinguish muscle mass from fat mass, so athletes and highly muscular individuals frequently score in the overweight range despite very low body fat. It also doesn't reflect fat distribution, which is a stronger predictor of metabolic risk than total weight. If your BMI is outside the healthy range and you're concerned, discuss it with a healthcare professional alongside waist circumference and other health indicators.

How to use it

  1. 1Enter your weight. Your weight in kilograms.
  2. 2Enter your height. Your height in centimetres.
  3. 3Read your BMI. The calculated BMI and its category.

How it works

The calculator divides your weight in kilograms by the square of your height in metres to give a Body Mass Index score. It then compares that score against the WHO cutoffs to place you in one of four categories: underweight, healthy weight, overweight or obese.

BMI is a screening tool and not a diagnosis. It doesn't distinguish muscle from fat, so athletic individuals often score in the overweight range despite low body fat percentages. Waist-to-height ratio (waist circumference divided by height, target below 0.5) is often a more useful supplement for assessing metabolic risk.

Formula

BMI = Weight (kg) ÷ Height (m)²

Weight in kilograms; Height converted from centimetres to metres before squaring.

Worked examples

75 kg, 175 cm tall

BMI = 75 ÷ 1.75² = 24.5 (healthy weight).

90 kg, 170 cm tall

BMI = 90 ÷ 1.70² = 31.1 (obese).

Frequently asked questions

What is BMI?

Body Mass Index — a weight-for-height ratio used as a screening tool for underweight, healthy weight, overweight and obesity categories.

What are the BMI categories?

Under 18.5 = underweight; 18.5–24.9 = healthy; 25–29.9 = overweight; 30+ = obese. These are WHO cutoffs.

Is BMI accurate for everyone?

No — it doesn't distinguish muscle from fat, so athletes often score 'overweight' despite being lean. It's a screening tool, not a diagnosis.

What are healthier alternatives?

Waist-to-height ratio and body fat percentage give more information about health risk than BMI alone.

Should I see a doctor about my BMI?

If your BMI is outside 18.5–24.9 and you're concerned, discuss it with a healthcare professional in the context of your overall health.

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