BMI Calculator

Calculate your Body Mass Index (BMI) and find out your weight category.

Weight (kg)

Height (cm)

Underweight <18.5 · Normal 18.5–24.9 · Overweight 25–29.9 · Obese ≥30

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How we work it out

BMI = weight(kg) ÷ height(m)²

weight

Body weight in kilograms

height

Height in metres

Reviewed by the QTNest tools desk

BMI Calculator — Calculate Your Body Mass Index in Seconds

Body Mass Index (BMI) is a widely used screening metric that relates your weight to your height to provide a general indication of whether your body weight falls within a healthy range. Our BMI Calculator supports both metric units (kilograms and centimetres) and imperial units (pounds and inches), giving you your numeric BMI value and the corresponding weight category instantly.

The standard BMI categories, as defined by the World Health Organisation, are: **Underweight** (below 18.5), **Normal weight** (18.5–24.9), **Overweight** (25–29.9), and **Obese** (30 and above). These thresholds are used by healthcare providers worldwide as an initial health screening baseline.

BMI is calculated using a simple formula: weight in kilograms divided by the square of height in metres (kg/m²). Our calculator handles the formula and the unit conversion automatically — just enter your measurements and read the result.

An important limitation to understand: BMI does not distinguish between muscle mass and body fat. A well-muscled athlete may show a BMI in the "overweight" range despite having low body fat and excellent cardiovascular health. Conversely, an older adult who has lost significant muscle mass may show a "normal" BMI despite having high body fat percentage. BMI is best used as a starting point, not a definitive health verdict. Always consult a qualified healthcare professional for a comprehensive health assessment.

How to use the BMI Calculator

Select your unit system: metric (kg/cm) or imperial (lbs/in).
Enter your height.
Enter your weight.
Your BMI score and weight category appear instantly.

Questions

What is a healthy BMI?

A BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.

Does BMI account for muscle mass?

No. BMI cannot distinguish between muscle and fat. Athletes often show a high BMI despite very low body fat. Use it as a screening tool, not a diagnosis.

Can I use imperial measurements?

Yes. The calculator supports both metric (kg/cm) and imperial (lbs/inches). Toggle between them with the unit selector.

Is BMI accurate for children?

Standard BMI categories are designed for adults aged 18 and over. For children, age- and sex-specific BMI-for-age percentiles are used instead.

What should I do if my BMI is outside the healthy range?

Speak with a GP or registered dietitian. BMI is one data point among many — a full health picture includes blood pressure, cholesterol, diet, and fitness.

Guides

10 Free Online Tools That Replace Paid Apps (No Signup Required)

Most paid utility apps charge for features that should be free. Here are ten browser-based tools that cover the most common everyday tasks — no account, no installation, no subscription.

BMI: What the Formula Actually Tells You — and What It Misses

BMI is everywhere — doctor visits, insurance forms, fitness apps. But it was invented by a Belgian mathematician in 1832 to study population averages, not to assess individual health. Here is what it does well, where it fails, and what to look at alongside it.

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