Our free BMI calculator tells you your Body Mass Index from your height and weight, and shows which healthy range you fall in. Enter your numbers in metric or imperial units and get an instant result with a clear explanation. No sign-up, and your health data never leaves your browser.
How to Use the BMI Calculator
- Enter your weight.
- Enter your height.
- Click Calculate to see your BMI number and category.
- Read the healthy weight range for your height under the result.
What Is BMI and What Do the Ranges Mean?
Body Mass Index is your weight in kilograms divided by your height in metres squared. Health organisations use the same ranges worldwide for adults: below 18.5 is underweight, 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight, and 30 or above is obese. BMI is a screening tool, not a diagnosis — it does not measure body fat directly, and muscular athletes can score high while being perfectly healthy. Used honestly, it is the quickest first check of whether your weight may be affecting your health.
How to Move Toward a Healthy BMI
Small habits beat strict diets. Walk 30 minutes a day, swap sugary drinks for water, and add protein and vegetables before cutting anything out. Aim to lose or gain slowly — about half a kilogram a week is sustainable. Recheck your BMI here every month rather than every day, because real change is gradual. If your BMI is very low or very high, or you have a medical condition, speak to a doctor before starting any plan: personal advice always beats a general calculator.
Frequently Asked Questions
Is this BMI calculator free?
Yes — free with no sign-up and no limits.
Does BMI apply to children?
Children and teenagers need age-and-sex percentile charts instead. This calculator uses the adult ranges.
Is BMI accurate for athletes?
Muscle weighs more than fat, so very muscular people can get a high BMI without excess fat. Waist size and body composition give a fuller picture.
Is my health data uploaded anywhere?
No. The calculation happens in your browser on your own device.
BMI for Asian Body Types
Research shows South Asian adults can face weight-related health risks at lower BMI values than Europeans, because body fat tends to gather around the waist. Some doctors therefore watch the 23 mark as an early warning for patients from Pakistan, India and Bangladesh rather than waiting for 25. Wherever your result falls, waist size adds the missing context: keep it under half your height as a simple rule. This calculator gives you the standard international result instantly, and knowing the stricter regional guidance helps you interpret it wisely for your own body.
When to Recheck and What Else to Track
Weigh yourself at the same time of day, ideally in the morning, and recheck your BMI monthly — daily numbers jump with water and meals and only discourage you. Track three more numbers alongside: waist size, how your clothes fit, and your energy through the day. If all four move in the right direction, your plan is working even when the scale pauses for a week. Plateaus are normal; consistency across months is what changes a BMI category for good.
Remember that BMI is the start of the conversation about healthy weight, not the whole story. Sleep, activity, food quality and family history all matter. Use your number here as a friendly monthly checkpoint, and let it motivate the small daily choices that move it in the right direction over time.
More free tools: find exact ages with the Age Calculator, convert measurements with the Unit Converter, or see all 24 free tools.
