What is a healthy BMI?

For adults, 18.5 to 24.9 is the healthy range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. The same cut-offs apply to men and women. Children and teenagers are scored against age and sex percentiles instead, so an adult BMI reading does not apply to them.

How do I calculate BMI by hand?

In metric, divide your weight in kilograms by your height in metres squared. Someone 1.75 m and 70 kg works out at 70 / (1.75 x 1.75) = 22.9. In imperial, multiply your weight in pounds by 703, then divide twice by your height in inches.

Is BMI accurate for athletes?

No. BMI counts every kilogram the same way, and muscle is denser than fat, so a lean rugby forward or powerlifter routinely scores 28 or higher while carrying single-digit body fat. If you train heavily, a tape measurement is the better read.

Does BMI use different numbers for men and women?

The formula and the thresholds are identical. Women carry more essential fat at any given BMI, roughly 10 percentage points more on average, which is one reason the number tells you about weight-for-height and not about body composition.

What BMI is considered obese?

30 and above. Clinicians often split that further: 30 to 34.9 as class I, 35 to 39.9 as class II, and 40 or more as class III. Some health services apply lower thresholds for people of South Asian, Chinese and other Asian descent, where metabolic risk climbs at a lower BMI.

What is a healthy weight for my height?

At 5 ft 5 in the healthy range is 112 to 150 lb, at 5 ft 9 in it is 126 to 169 lb, and at 6 ft 0 in it is 137 to 184 lb. The same ranges apply to men and women. Every weight inside the band scores as healthy, so the range is the answer, not a single number within it.

What does a BMI of 25 mean?

It is the first point of the overweight band, which runs from 25 up to 30. Nothing changes about your body between 24.9 and 25.0; the line is an administrative cut across a continuous risk curve. At 25 exactly, waist measurement and body composition tell you far more than the BMI does.

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BMI Calculator for Adults

Calculate adult BMI in kg/cm or pounds/feet. See your position on the BMI scale, screening category and weight range, then copy the results.

BMI Calculator

Body Mass Index. A quick screen for whether your weight sits in a healthy range for your height.

Weight

Height

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Healthy weight range

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How to calculate BMI

Body mass index (BMI) = weight in kilograms ÷ height in metres squared. For pounds and inches, the commonly rounded formula is 703 × weight in pounds ÷ height in inches squared. Those two routes disagree slightly. This calculator converts your imperial inputs to metric before calculating, so expect a small difference from the rounded 703 formula if you check the sum by hand.

The categories below are for adults aged 20 and older, following the CDC’s adult BMI guidance. Children and teenagers need age- and sex-specific interpretation.

Adult BMI chart

Adult BMI screening categories
BMI	Category
Below 18.5	Underweight
18.5 to below 25	Healthy weight
25 to below 30	Overweight
30 or higher	Obesity

Categories use the unrounded BMI, and the display rounds to one decimal place. A result near a boundary can therefore show you 25.0 while the underlying figure still sits a fraction below 25. Whatever the number does, it screens and does not diagnose, and the diagnosis is your doctor’s to make.

Worked BMI examples

70 kg at 175 cm: convert height to 1.75 m, square it to get 3.0625, then divide 70 by 3.0625. BMI is 22.86, shown as 22.9.

200 lb at 5 ft 11 in: height is 71 inches. Using the rounded imperial formula, 703 × 200 ÷ 71² gives 27.9 after rounding.

What the weight range means

The tool multiplies your squared height in metres by 18.5 and 24.9 to show an illustrative weight range inside the adult healthy-weight BMI category. At 175 cm that works out at about 56.7 to 76.3 kg. Nearly 20 kg separates the bottom of that band from the top, and every weight in between carries the same label. Picking the figure that suits you takes information no formula has, which is where your doctor comes in.

For a comparison with four historical height-based formulas, use the ideal weight calculator. For a tape-based body-composition estimate, use the body fat calculator.

What BMI cannot tell you

BMI reads your total mass. Muscle, fat and where that fat is stored all arrive on the display as the same kilogram, so a muscular adult can land in the same category as someone carrying a very different body composition. The longer argument over the index, and which parts of it hold up, is set out in is BMI outdated. Your age, your medical history and your other health measures all count alongside the number, and the CDC’s explanation of BMI and health assessment fills in that context.

Do not use these adult categories for children or teenagers, and do not use the result to set a pregnancy weight target. Both need a clinician. For any medical decision, take the number to someone who can assess more than your height and your weight.

Read your BMI result on the scale

The marker shows your position on a BMI scale from 10 to 45, and the text names the screening category. At 30 and above it splits that into class 1 (30 to below 35), class 2 (35 to below 40) and class 3 (40 and above), following the CDC adult categories. A number off the end of the chart still shows, printed above the scale.

The calculation uses your full input values before rounding, so near a boundary you want to read the category and the two-decimal detail together. 24.96 rounds to 25.0 at one decimal place while sitting below the 25 boundary. Your body fat percentage and any health condition you have are measured elsewhere, by other tools.

Copy or print your calculation

Open How your result is calculated and you get the height conversion, the squaring step, the division and the two healthy-range bounds, all worked through with your own figures. The steps run the same equation as the headline result, with intermediate numbers rounded so they read cleanly.

Copy results puts your inputs, the labelled results, the calculation steps and the notes on your clipboard. Print / save PDF opens a report preview and then your browser’s print dialogue, where Save as PDF is usually one of the options. Read the report before you send it to anyone, because it carries the measurements you typed in. Reset example puts the sample values back and leaves your unit choices alone. All of this happens in your browser, and the tool keeps no history of your calculations.

Common questions

Is the BMI formula different for men and women?

The adult arithmetic is identical. Your height and your weight produce the number, and reading it still takes your own context.

Can I calculate BMI in kilograms and centimetres?

Yes. Choose kilograms and centimetres. The calculator converts centimetres to metres before squaring the height.

Why does my BMI change slightly between calculators?

Input rounding, conversion precision and rounding the final number all open up small gaps. Compare the same exact height and weight in the same units before you treat a 0.1 difference as a problem.

Does a healthy-range BMI guarantee good health?

No. BMI is one screening measure, and it has no visibility of your fitness, your diet, your blood pressure or your bloods.

Can this calculator be used for children?

The formula will produce a number for anyone, but these categories only apply from age 20. Children and teenagers need a paediatric BMI-for-age tool that accounts for growth.

Written and maintained by Rowan Hale, the site author’s pen name. Updated September 13, 2026. No medical or dietetic qualification is claimed. Read our editorial policy or report a calculation error.

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