What formula does the BMI Calculator use?

It uses the standard WHO formula: BMI = weight in kilograms divided by height in metres squared. In US units, weight and height are converted to kilograms and centimetres first, then the same formula is applied.

What BMI range counts as a healthy weight?

A BMI from 18.5 to 24.9 is classified as the normal (healthy) range by the WHO. The BMI Calculator also shows the actual weight range, in kilograms or pounds, that corresponds to 18.5–24.9 at your specific height.

Is the BMI Calculator accurate for athletes or very muscular people?

BMI does not distinguish muscle from fat, so athletes and very muscular people can show a higher BMI despite having low body fat. Use the Body Fat Calculator alongside it for a more complete picture.

Does the BMI Calculator work in pounds and inches?

Yes. Switch the unit toggle to US and enter your weight in pounds and your height in feet and inches — the calculator converts everything to metric internally before computing BMI.

Is the BMI Calculator's result medical advice?

No. It gives a general estimate based on a standard formula. It is not a diagnosis and does not replace guidance from a doctor or other qualified healthcare professional.

Is my weight and height data uploaded when I use the BMI Calculator?

No. The BMI Calculator runs entirely in your browser. The numbers you type are used only to compute the result on your device and are never sent to ArrayKit or anywhere else.

BMI Calculator Online

Calculate your body mass index and see the healthy weight range for your height, right in your browser. A general estimate, not medical advice.

The BMI Calculator runs entirely in your browser. The weight and height you enter never leave your device and nothing is uploaded to ArrayKit. Results are a general estimate, not medical advice.

Open the Healthy Weight Calculator

About BMI Calculator

BMI Calculator works out your body mass index from your weight and height, then places it on the WHO categories of underweight, normal, overweight and obese. Switch between Metric (kilograms and centimetres) and US (pounds and feet/inches) units, and the tool shows your BMI to one decimal place alongside the healthy weight range for your exact height, calculated at a BMI of 18.5 to 24.9. It is a quick way to check where you fall on a standard weight-for-height scale before a checkup, when tracking fitness progress, or when comparing against a target range. Everything computes instantly on your device — your weight and height are never uploaded. BMI is a general estimate from a standard formula and does not replace medical advice from a healthcare professional.

Features

Calculates BMI from weight and height using the standard WHO formula
Toggle between Metric (kg/cm) and US (lb/ft-in) units
Classifies your result as underweight, normal, overweight or obese
Shows the healthy weight range for your exact height (BMI 18.5–24.9)
Copy a plain-text summary of your BMI and healthy range in one click
Instant results as you type, with no page reloads
Clear error message for missing or invalid weight or height
Runs entirely in your browser — your figures never leave your device

How to use the BMI Calculator

Choose Metric or US units
Enter your weight and height
Read your BMI, category, and healthy weight range
Copy the summary or adjust the numbers to see how BMI changes

Example

Input

70 kg, 175 cm

Output

BMI: 22.9 (Normal)

70 ÷ 1.75² = 22.9, which falls in the WHO "Normal" range of 18.5–24.9.

Common errors & troubleshooting

BMI Calculator shows an error even though numbers were entered. — Make sure weight and height are both greater than zero — in US mode, fill in at least the feet or inches field for height.
Result looks way too high or too low after switching units. — Switching between Metric and US keeps each unit's fields separate, so re-enter your weight and height in the newly selected unit system.
Height entered in metres instead of centimetres gives a huge BMI. — The Metric height field expects centimetres (e.g. 175, not 1.75) — the BMI Calculator converts to metres internally.
BMI looks normal but body composition still feels off. — BMI does not account for muscle mass or body fat distribution — pair it with the Body Fat Calculator for a fuller picture.

Frequently asked questions

What formula does the BMI Calculator use?: It uses the standard WHO formula: BMI = weight in kilograms divided by height in metres squared. In US units, weight and height are converted to kilograms and centimetres first, then the same formula is applied.
What BMI range counts as a healthy weight?: A BMI from 18.5 to 24.9 is classified as the normal (healthy) range by the WHO. The BMI Calculator also shows the actual weight range, in kilograms or pounds, that corresponds to 18.5–24.9 at your specific height.
Is the BMI Calculator accurate for athletes or very muscular people?: BMI does not distinguish muscle from fat, so athletes and very muscular people can show a higher BMI despite having low body fat. Use the Body Fat Calculator alongside it for a more complete picture.
Does the BMI Calculator work in pounds and inches?: Yes. Switch the unit toggle to US and enter your weight in pounds and your height in feet and inches — the calculator converts everything to metric internally before computing BMI.
Is the BMI Calculator's result medical advice?: No. It gives a general estimate based on a standard formula. It is not a diagnosis and does not replace guidance from a doctor or other qualified healthcare professional.
Is my weight and height data uploaded when I use the BMI Calculator?: No. The BMI Calculator runs entirely in your browser. The numbers you type are used only to compute the result on your device and are never sent to ArrayKit or anywhere else.

Related tools

Healthy Weight Calculator — Find the healthy weight range for your height from the normal BMI band.
Body Fat Calculator — Estimate body fat percentage with the US Navy tape measurement method.
Ideal Weight Calculator — Estimate ideal body weight with the Devine, Robinson, Miller and Hamwi formulas.
BMR Calculator — Estimate your basal metabolic rate — the calories your body burns at rest.
Calorie Calculator — Estimate daily calories to maintain, lose or gain weight from your stats.
Body Surface Area Calculator — Estimate body surface area (BSA) with Mosteller, Du Bois and other formulas.