BMI Calculator
Find your Body Mass Index and see where it sits on the standard healthy-range scale.
Result
Fill in the inputs to see your result.
Inputs
Try an example
Formula
BMI = weight (kg) ÷ height (m)²
For imperial inputs we convert pounds to kilograms (×0.4536) and inches to meters (×0.0254) before applying the same formula.
How it works
BMI is a screening tool that estimates whether your weight is in a healthy range relative to your height. It's quick and useful at a population level, but it doesn't directly measure body fat or distinguish muscle from fat.
Common mistakes
- Mixing units — entering height in cm but weight in pounds.
- Treating BMI as a diagnosis. It's a screening signal, not a verdict.
- Using adult ranges for children or teens — they have age-specific charts.
- Ignoring muscle mass — athletes often score 'overweight' but have low body fat.
Source & methodology
Healthy ranges follow World Health Organization adult cut-offs: underweight <18.5, healthy 18.5–24.9, overweight 25–29.9, obese ≥30.
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Last updated
The data and formulas powering this calculator were last reviewed on Jan 15, 2025.
Calcxo gives you the answer plus the reasoning behind it.
Quick answer
BMI Calculator: in one paragraph
BMI (Body Mass Index) is your weight divided by your height squared. It's a quick screening number — not a diagnosis — that tells you whether your weight sits in a generally healthy range for your height.
What this calculator does
The BMI calculator takes your height and weight and returns a single number that compares you to a standard healthy range. It also shows you the weight range that would put you inside the healthy band, so you can see how far away (if at all) you are from it.
Why people use it
- Get a fast, reproducible health snapshot you can track over time.
- Have a shared number to discuss with a doctor or trainer.
- Compare your weight to public-health guidelines without guesswork.
- See the healthy weight range for your specific height.
A worked BMI calculation
A concrete walkthrough you can follow line by line.
Someone who is 175 cm tall and weighs 72 kg wants to check their BMI.
1. Convert height to meters
175 cm ÷ 100 = 1.75 m
2. Square the height
1.75 × 1.75 = 3.0625
3. Divide weight by that
72 ÷ 3.0625 ≈ 23.5
Result
BMI ≈ 23.5 — inside the standard healthy range of 18.5 to 24.9.
When to use this calculator
- You want a general health screening number for an adult of average build.
- You're tracking weight changes month over month and want a normalized metric.
- You're filling in an intake form that asks for BMI.
- Avoid relying on BMI alone if you're highly muscular, pregnant, very tall or short, or under 18 — it tends to misclassify those groups.
Common mistakes
- Mixing units — entering height in centimeters but weight in pounds.
- Reading BMI as a body-fat percentage. It isn't one.
- Applying adult BMI ranges to children or teens — they have different age- and sex-adjusted charts.
- Treating one BMI reading as a verdict instead of a trend.
Quick questions
- Is BMI accurate?
- BMI is accurate as a population-level screening tool but rough at the individual level. It can't tell muscle from fat, so very muscular people often score 'overweight' even when they're lean.
- What's a healthy BMI?
- For most adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese.
Terms used on this page
- BMI
- Body Mass Index — weight in kilograms divided by height in meters squared.
- Healthy range
- For adults, a BMI between 18.5 and 24.9.
Learn more
Deeper reads from the Calcxo learn library.