BMI Calculator
Enter your height and weight in metric or imperial units to get your Body Mass Index (BMI) and the corresponding weight category.
Example
Someone 175 cm tall weighing 70 kg has a BMI of 22.9, which falls in the Normal weight range (18.5–24.9).
How it works
BMI is weight divided by height squared. In metric that's kg ÷ m²; in imperial it's 703 × lb ÷ in². The result is mapped to the standard WHO categories: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese.
Good to know
This BMI Calculator turns two numbers you already know — your height and weight — into a single Body Mass Index figure and the weight category it falls into. It accepts either metric (centimetres and kilograms) or imperial (feet, inches and pounds) input, does the maths in your browser, and shows the result instantly without sending anything to a server. It is aimed at adults who want a quick population-level screening number rather than a clinical assessment.
Most people reach for a BMI number at the start of a fitness plan, before a check-up, when comparing a reading over time, or simply out of curiosity after stepping off the scale. Because the calculation is deterministic, the value you get here will match any other correctly-implemented BMI tool for the same inputs — the difference is that this one keeps your figures local and works once the page has loaded, even offline.
Read the output as a position on a continuous scale, not a verdict: the index is mapped to four WHO bands (under 18.5, 18.5–24.9, 25–29.9, and 30+), and a number sitting near a boundary can shift categories with a kilogram or two. Pay attention to the decimal as much as the label, and remember the index rises sharply when height is entered slightly wrong, since height is squared in the formula.
One practical caveat: BMI uses only mass and height, so it cannot tell muscle from fat or account for frame size, age, pregnancy, or athletic build, and the adult bands do not apply to children or teens. Use it as a starting point to track change over weeks rather than as a stand-alone measure of health, and double-check by entering your height in the exact units the tool expects before reading too much into a borderline result.
Frequently asked questions
What are the BMI categories?
Underweight: below 18.5 · Normal: 18.5–24.9 · Overweight: 25–29.9 · Obese: 30 and above. These are the standard WHO ranges for adults.
Is BMI accurate for everyone?
BMI is a useful screening tool but doesn't distinguish muscle from fat. Very muscular people may read as 'overweight' despite low body fat. Treat it as a guide, not a diagnosis.
Does it work in pounds and feet?
Yes — switch to Imperial to enter height in feet and inches and weight in pounds; the formula adjusts automatically.
Is my data uploaded anywhere?
No. Everything is calculated in your browser with JavaScript — nothing is sent to a server, so it's private and works offline once loaded.
Is this calculator free?
Yes, completely free with no sign-up and no limits.
People also ask
What is a healthy BMI range for adults?
Under the standard WHO classification, a BMI between 18.5 and 24.9 is labelled the normal range for most adults. Values below 18.5 are categorised as underweight and 25 or above as overweight or obese.
How do I calculate BMI manually?
In metric, divide your weight in kilograms by your height in metres squared (kg ÷ m²). In imperial, multiply your weight in pounds by 703 and divide by your height in inches squared (703 × lb ÷ in²).
Is BMI different for men and women?
The BMI formula and the standard adult category thresholds are the same regardless of sex. Body composition does differ between men and women on average, which is one reason BMI is treated as a general screening figure rather than a precise body-fat measure.
Why does my BMI seem high even though I'm fit?
BMI is based only on height and weight, so it counts muscle the same as fat. People with high muscle mass, such as athletes or weight trainers, can fall into the overweight band despite low body fat.
Does BMI apply to children and teenagers?
The fixed adult bands used here do not apply to those under 18. Children and teens are typically assessed with age- and sex-specific BMI-for-age percentile charts instead of fixed numeric ranges.
What is considered a dangerous BMI level?
BMI values of 30 and above fall in the obese category, and very high or very low readings are generally associated with greater health risk in research. BMI alone is a screening signal, not a diagnosis, so it should be interpreted alongside other measures.
How accurate is BMI as a health measure?
BMI is a quick, reproducible screening tool but it cannot distinguish fat from muscle or show where fat is stored. It is most useful for tracking changes over time or comparing across large groups rather than judging an individual's health on its own.
What other measurements are used alongside BMI?
Common companions include waist circumference, waist-to-height ratio, body-fat percentage, and blood markers. These add information about fat distribution and metabolic health that BMI by itself does not capture.
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