Your Body Mass Index (BMI) is a quick, widely used screening number that estimates whether your weight is in a healthy range for your height. It is easy to calculate and a useful starting point for thinking about your health. Here is what BMI means, how to calculate it, and how to read your result.
What is BMI and how is it calculated?
BMI is your weight divided by the square of your height. In metric terms it is kilograms divided by metres squared. The standard categories are: under 18.5 (underweight), 18.5–24.9 (healthy weight), 25–29.9 (overweight) and 30 or above (obese). You do not need to do the maths by hand — a calculator does it instantly.
Calculate your BMI instantly
The free BMI Calculator on apps2help.com supports both metric and imperial units. Enter your height and weight to see your BMI, your category on a visual gauge, and your ideal healthy weight range — all calculated privately in your browser.
- Open the BMI Calculator.
- Choose metric or imperial units and enter your height and weight.
- Read your BMI, your category, and your ideal weight range.
Understanding the limits of BMI
BMI is a helpful general guide, but it is not a complete picture of health. It does not distinguish muscle from fat, so very muscular people may read as overweight, and it does not account for age, sex or fat distribution. Treat BMI as one signal among many, and consult a healthcare professional for personalised advice.
Frequently asked questions
What is a healthy BMI? Generally 18.5 to 24.9, though individual factors matter.
Does the tool support imperial units? Yes — both metric and imperial.
Is my data private? Yes, everything is calculated in your browser. See our Privacy Policy.
This information is for general educational purposes and is not medical advice.
Check yours: use the free BMI Calculator now.
Reading the number without over-reading it
Body mass index is a ratio: weight in kilograms divided by height in metres squared. Someone 1.65 m tall weighing 62 kg calculates 62 ÷ 2.7225 = 22.8. That is genuinely all it is. It was designed in the nineteenth century to describe populations, and it was only adopted for individual screening much later because it needs two measurements anyone can take.
Understanding that origin is the most useful thing here, because it explains the limitation directly: a measure built to describe averages across thousands of people tells you relatively little about one specific person.
Working out your healthy weight range instead
Rather than calculating an index and looking it up, it is often more useful to run the formula backwards and find the weight range that corresponds to the healthy band for your height. Multiply the lower and upper thresholds by your height in metres squared.
| Height | Height squared | 18.5 to 24.9 | 18.5 to 22.9 (lower Asian threshold) |
|---|---|---|---|
| 1.55 m | 2.40 | 44.4 – 59.8 kg | 44.4 – 55.0 kg |
| 1.60 m | 2.56 | 47.4 – 63.7 kg | 47.4 – 58.6 kg |
| 1.65 m | 2.72 | 50.4 – 67.8 kg | 50.4 – 62.3 kg |
| 1.70 m | 2.89 | 53.5 – 72.0 kg | 53.5 – 66.2 kg |
| 1.75 m | 3.06 | 56.6 – 76.2 kg | 56.6 – 70.1 kg |
| 1.80 m | 3.24 | 59.9 – 80.7 kg | 59.9 – 74.2 kg |
Notice how wide each range is — typically fifteen to twenty kilograms. A range that broad is a hint about how coarse the measure is. Two people at opposite ends of the same healthy band look entirely different.
Why some guidelines use lower thresholds
Indian and several other Asian clinical guidelines treat 23 rather than 25 as the point where overweight begins. This reflects consistent research findings that at any given index, body fat percentage tends to be higher and more concentrated around the abdomen in South and East Asian populations, with associated metabolic risk appearing at lower readings. Which threshold applies to you is a question for a doctor who knows your history, not something a calculator can decide.
Measure it properly or do not bother
Height is squared in the formula, so height errors are amplified. Being two centimetres out shifts the result by roughly 0.6 points, which is enough to move someone across a category boundary. Measure without shoes, heels and back against a wall, looking straight ahead, ideally in the morning when the spine is least compressed. Weigh at a consistent time in similar clothing. Normal day-to-day variation of one to two kilograms is water and food, not fat, so single readings mean very little — a trend over six to eight weeks means something.
The measurement that adds the most
Waist circumference, divided by height, aiming for below roughly 0.5. Measure at the midpoint between the lowest rib and the top of the hip bone, standing relaxed, breathing out normally, tape snug but not compressing the skin. This captures abdominal fat, which the index cannot distinguish at all, and it is the deposit most closely associated with metabolic risk. Someone whose index sits in the overweight band but whose waist ratio is well under 0.5 is in a different position from someone with the same index and a ratio of 0.6.
Where the number is simply the wrong tool
- Muscular people. Muscle is denser than fat, so athletes routinely register as overweight or obese with low body fat.
- Older adults. Muscle mass declines with age while fat rises, so an unchanged reading over twenty years can hide a substantial change in composition.
- Children and teenagers. Assessed against age-and-sex percentile charts instead, because normal body composition shifts throughout growth.
- Pregnancy. The standard bands do not apply.
- Very tall or very short people. Dividing by height squared distorts at both extremes.
What to do with the result
Treat it the way you would treat a single blood pressure reading: a prompt to look further, not a conclusion. If it falls outside the healthy band, the useful follow-up questions are about your waist measurement, how your weight has trended over one to two years, your activity level, your blood pressure and blood sugar, and your family history. Those together form a picture that a single ratio cannot.
This is general educational information, not medical advice. It cannot account for your individual circumstances and is not a substitute for assessment by a qualified healthcare professional. If a result concerns you, please speak with a doctor rather than acting on a number from a web page.