Useful Utilities

BMI Calculator

Find your body mass index from height and weight in metric or imperial units, see where you fall on the WHO seven-band scale, and read the weight range that a BMI of 18.5 to 25 implies at your height.

Fill in the values and calculate

Measurement systemPick the units your measurements are inDefault Metric (cm, kg)
Height (cm) (cm)Used in metric modeDefault 170
Height (feet) (ft)Used in imperial modeDefault 5
Height (extra inches) (in)Used in imperial modeDefault 7
Weight (kg) (kg)Used in metric modeDefault 70
Weight (lb) (lb)Used in imperial modeDefault 154

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About BMI Calculator

The body mass index is a unitless ratio of mass to height squared: BMI = kilograms ÷ metres². Because the units cancel, the same number describes the same body shape whether you measured in centimetres and kilograms or in inches and pounds — this calculator converts imperial inputs at one inch = 2.54 cm and one pound = 0.4536 kg so both modes agree.

Classification follows the World Health Organization's seven-band scale used in population health statistics: below 16 is severe underweight, 16 to 18.5 mild underweight, 18.5 to 25 the healthy band, 25 to 30, 30 to 35 and 35 to 40 mild through severe overweight, and 40 and above extreme. The healthy-weight-range card runs the same formula backwards: mass = BMI × height² evaluated at BMI 18.5 and 25 for your exact height, in whichever units you selected.

BMI is a screening number, not a fitness goal. It carries no information about frame size, muscle mass or posture, and the WHO cut-points describe statistical distributions rather than any individual. Read the number alongside waist-to-height ratio and your own measurements before drawing conclusions about health or leanness.

Questions about BMI Calculator

How is BMI calculated?

BMI is weight divided by height squared, with weight in kilograms and height in metres. Someone weighing 70 kg at a height of 1.70 m gets 70 ÷ 1.70² = 24.2. Entering the same body in feet and pounds gives the same result after unit conversion.

What weight corresponds to a healthy BMI?

Multiply the BMI band by your height squared. A person 1.70 m tall has a height² of 2.89 m², so BMI 18.5 equals 53.5 kg and BMI 25 equals 72.3 kg. This calculator performs that arithmetic for your height and shows the range in your chosen units.

Is a good BMI the same as being healthy?

No. BMI is a screening ratio: it ignores frame size, where weight is carried and body composition, so two people with identical BMI can look quite different. Researchers often treat a waist-to-height ratio below 0.5 as a better predictor of cardiometabolic risk, and children and older adults follow different norms entirely.

Why do metric and imperial results differ slightly?

The formula is identical in both modes; the final decimal can shift because the displayed inputs are rounded values. Enter your measurements in one system and stay with it, and treat differences below 0.1 BMI as measurement noise.

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