BYTETOOLS

BMI Calculator

Calculate your Body Mass Index from height and weight in metric (cm/kg) or imperial (ft-in/lbs) units and see your WHO category with a color-coded badge.

24.2
Your BMI
Normal weightWHO category

Healthy weight range for your height (BMI 18.5–24.9)

53.5 kg to 72.0 kg

BMI is a screening measure, not a diagnosis — muscle mass, age and body composition also matter.

What is the BMI Calculator?

The ByteTools BMI Calculator works out your Body Mass Index from height and weight, in either metric (centimetres and kilograms) or imperial (feet, inches and pounds) units.

  • Metric and imperial units with instant toggle
  • WHO categories with colour-coded badge
  • Shows the healthy weight range for your height
  • Live results — no calculate button
  • 100% private — health data never leaves your browser
  • Free, no sign-up required

How to use the BMI Calculator

  1. 1

    Choose your unit system: metric (cm, kg) or imperial (ft + in, lbs).

  2. 2

    Enter your height.

  3. 3

    Enter your weight.

  4. 4

    Read your BMI value and WHO category instantly, plus the healthy weight range for your height.

About the BMI Calculator

The ByteTools BMI Calculator works out your Body Mass Index from height and weight, in either metric (centimetres and kilograms) or imperial (feet, inches and pounds) units. Your BMI value appears instantly together with the World Health Organization category — underweight, normal weight, overweight or obese — highlighted with a colour-coded badge.

BMI is a quick screening measure used by doctors and fitness professionals to assess whether weight is in a healthy range for a given height. It is a starting point rather than a diagnosis, but tracking it over time is a simple way to monitor progress.

Height and weight are processed entirely in your browser — nothing is uploaded or saved — so your health data stays completely private.

Frequently asked questions

How is BMI calculated?

BMI equals weight in kilograms divided by height in metres squared: BMI = kg ÷ m². For imperial units the formula is 703 × pounds ÷ inches². A 70 kg person who is 1.75 m tall has a BMI of 70 ÷ 3.0625 ≈ 22.9.

What is a healthy BMI range?

The WHO classifies a BMI of 18.5 to 24.9 as normal weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. The calculator badges your result with the matching category automatically.

Is BMI accurate for athletes and bodybuilders?

Not always. BMI cannot distinguish muscle from fat, so very muscular people often register as overweight despite low body fat. For athletes, measures like body-fat percentage or waist-to-height ratio give a fuller picture.

Does BMI differ for men and women?

The standard adult BMI formula and WHO categories are the same for both sexes. Women naturally carry slightly more body fat at the same BMI, and for children and teens age- and sex-specific percentile charts are used instead.

What weight should I be for my height?

Multiply your height in metres squared by 18.5 and by 24.9 to get the healthy range. At 1.70 m that is roughly 53.5 kg to 72 kg. This calculator displays your personal healthy range automatically.

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