BMI Calculator
Body Mass Index
Body Mass Index Runs locally in your browser
Category: Normal weight
Under 18.5 underweight · 18.5 to 24.9 normal · 25 to 29.9 overweight · 30 and above obese
Weight: 70.0 kg Height: 175.0 cm BMI: 22.9 Category: Normal weight
About the
The BMI Calculator takes a weight in kilograms and a height in metres and returns the Body Mass Index along with the standard category. BMI is weight divided by height squared, so it is a screening number rather than a diagnosis: it says nothing about muscle, bone density or fat distribution, which is why a heavily muscled person can land in the overweight band while carrying very little fat. It remains useful as a population-level indicator and as a quick personal reference, and it is the number most health forms ask for.
Where people use the
- Checking a figure for a health or insurance form.
- Converting imperial measurements into a metric BMI.
- Tracking a general trend over months rather than days.
- Sanity-checking a number produced by another app.
How to use the
- 1
Choose your units
Switch between metric, kilograms and centimetres, and imperial, pounds, feet and inches. The result is the same either way.
- 2
Enter weight and height
Fill in the two or three fields. The result updates as you type, so there is no calculate button to press.
- 3
Read the category
Under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is obese. The thresholds are shown under the result.
- 4
Copy the summary
The result block contains the weight and height in metric along with the BMI and its category, ready to paste into a form or a note.
Tips and best practices
- Measure in the morning under consistent conditions if you are tracking a trend.
- Treat BMI as one signal, not a verdict; waist-to-height ratio adds useful information.
- For clinical decisions, speak to a professional rather than relying on a screening number.
Frequently asked questions
What is the formula?
BMI equals weight in kilograms divided by height in metres squared. At 70 kilograms and 1.75 metres that is 70 divided by 3.0625, which is 22.9.
Why does BMI say I am overweight when I am fit?
Because BMI cannot distinguish muscle from fat. Muscle is denser than fat, so people with high lean mass, particularly athletes, regularly score in the overweight band. Waist measurement or body-fat percentage is more informative for them.
Is the same scale used everywhere?
The formula is the same worldwide, but some countries adjust the category thresholds for their population. Several Asian countries use lower cut-offs because health risks appear at lower BMI in those populations.
Does it work for children?
No. Children need age and sex adjusted percentiles, because body composition changes through growth. Use a paediatric growth chart instead of an adult BMI number.
How precise is the result?
To one decimal place, which is more precision than the input usually justifies. Body weight fluctuates by a kilogram or more over a day, so treat the number as a rough indicator rather than a measurement.
Is my data recorded?
No. The arithmetic happens in your browser and nothing is transmitted or stored.