FormatFlow

No tool matches “”

Try a format (“webp”, “mp3”) or a verb (“merge”, “compress”).

PDF toolsImage toolsVideo toolsAll tools

Loading index

↵to open

Calculators · Updated October 19, 2026

BMI Calculator — Metric and Imperial

You can calculate your body mass index from metric or imperial height and weight, see the adult BMI category it falls into and the healthy weight range for your height.

Runs in your browserFree · No sign-up · No watermark
BMIRuns in your browser
Loading the tool…

Everything runs locally in this tab. No file is uploaded while the tool loads.

This tool runs in your tab. Nothing is uploaded and no copy is stored.

How files are handled

At a glance

Works with
BMI
Processing
In your browser
Price
Free, no account
Updated
October 19, 2026
All Calculators

About BMI Calculator

Body mass index is a single number that compares weight with height, and it is the measure most clinics and health forms use for a first screening. Working it out means converting units correctly — centimetres to metres, or pounds and inches into the imperial formula — and then reading the score against the right band for adults. This calculator does both in one place.

It shows the BMI, the category and the weight range that would put you in the healthy band at your height, which is often more useful than the number itself. It also keeps the caveat in view: BMI cannot distinguish muscle from fat and is not a diagnosis. Metric and imperial inputs are both supported, with the conversion shown under the result.

What this tool does

The details that matter when you use BMI Calculator for real work.

  • Metric and imperial input

    Enter centimetres and kilograms, or feet, inches and pounds; the tool uses the formula that matches your units and shows the converted measurements.

  • Adult category band

    See which adult band the rounded BMI falls into, from underweight through the three obesity classes, with the exact range for each band.

  • Healthy weight range

    The tool calculates the weight range that corresponds to a BMI of 18.5 to 24.9 at your height, in whichever unit system you used.

  • Working shown

    The formula, your substituted numbers and the rounded BMI are printed under the result so the calculation can be checked line by line.

  • Live results with inline errors

    BMI updates as you type once both height and weight are valid, and out-of-range or non-numeric entries are explained next to the field.

  • Clear medical caveat

    A permanent note explains that BMI is a screening indicator, not a diagnosis, and lists the groups the adult bands do not apply to.

How to use BMI Calculator

No account, no installation — the whole job happens in this browser tab.
  1. 01

    Choose your units

    Select Metric for centimetres and kilograms, or Imperial for feet, inches and pounds.

  2. 02

    Enter your height and weight

    Type your height and current weight. The inches field can be left empty when your height is a whole number of feet.

  3. 03

    Read the BMI

    The headline is your BMI to one decimal place, labelled with the adult category it falls into.

  4. 04

    Check the healthy range

    The panel below shows the weight range that would give a BMI between 18.5 and 24.9 at your height.

  5. 05

    Use the result with caution

    Treat the number as a screening indicator, read the caveats, and discuss any concern with a qualified health professional.

How this tool works

Works with
BMI
Processing
Client-side, in your browser. Nothing is uploaded.
Requirements
Chrome, Edge, Firefox or Safari · Height and weight in metric or imperial units

Limitations worth knowing

  • BMI is a screening indicator, not a diagnosis, and it cannot distinguish muscle from fat or show where body fat is stored.
  • The adult category bands do not apply to children, pregnant people, athletes or adults over 65.
  • The healthy weight range is calculated from BMI alone; it ignores frame size, body composition and medical history.

Privacy and file handling

Height and weight are processed entirely in your browser, and the BMI is calculated locally with JavaScript. Nothing you type is uploaded, stored or logged, and no request is made while you use the tool.

Read the full privacy policy

BMI Calculator FAQ

Short, direct answers to the questions people ask before using this tool.
What is a healthy BMI?
For adults, a BMI between 18.5 and 24.9 is classified as healthy weight. Below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30 or above is obesity, split into three classes in the table on this page.
Does BMI tell me how much body fat I have?
No. BMI only compares weight with height, so it cannot separate muscle, bone, water and fat. A muscular athlete can sit in the overweight band while carrying little fat, and an older adult can have a normal BMI with low muscle mass.
Why is my BMI different from the one my doctor calculated?
The formula is the same, but results differ with rounding, measured versus reported height, time of day and clothing. Clinicians also look at waist circumference and body composition, so a small difference between readings is normal.
Which BMI formula does this calculator use?
Metric: kilograms divided by height in metres squared. Imperial: 703 times pounds divided by height in inches squared. Both produce the same score when the measurements describe the same person.
Is BMI accurate for children and teenagers?
Not with the adult bands used here. Children and teenagers are assessed with age- and sex-specific growth charts, so a child's BMI has to be interpreted by a paediatric professional. This tool is intended for adults.
Should I use a BMI calculator while pregnant?
No. BMI is not a useful measure during pregnancy because weight gain is expected and the adult bands do not apply. Discuss weight and health during pregnancy with a midwife or doctor.
Why does the BMI score change with shoes on?
A centimetre or two of shoe height is enough to move the BMI by a fraction of a point, which matters when tracking a trend. Measure without shoes and at a similar time of day so repeat readings are comparable.
Is my height and weight stored?
No. Everything is calculated in your browser and nothing is uploaded, saved in local storage or logged. Closing the page clears what you typed, and no health data is sent to FormatFlow.
What should I do if my BMI is outside the healthy range?
A single reading is not a verdict. BMI can be high because of muscle, and low for many reasons, while health involves more than one number. Use the result as a prompt for a conversation with a qualified professional rather than a reason to change diet or medication alone.