BMI Calculator in kg and cm: Formula and Examples

A BMI calculator in kilograms and centimeters uses your weight in kg and height in cm to calculate body mass index, a height-adjusted weight measure. Enter weight and height to get a BMI value; the calculator also shows the standard adult categories, which are screening ranges rather than a diagnosis.

Formula

The standard metric formula is:

BMI = weight in kilograms ÷ (height in meters × height in meters)

In symbols, BMI = W / H², where W is body weight in kilograms (kg) and H is height in meters (m). Because the calculator takes height in centimeters, it first converts centimeters to meters by dividing by 100. BMI is conventionally reported in kg/m², although the unit is often omitted when stating a result.

For the calculator inputs, the same formula is weight / ((height / 100)²). Use your current weight and standing height as measured, not a height in centimeters entered as though it were meters.

Worked Example

Using the calculator’s defaults—weight 70 kg and height 170 cm:

1. Convert height to meters: 170 ÷ 100 = 1.70 m.
2. Square the height: 1.70 × 1.70 = 2.89 m².
3. Divide weight by squared height: 70 ÷ 2.89 = 24.221…
4. Round to one decimal place: BMI = 24.2 kg/m².

The displayed value is rounded for readability; category decisions should use the underlying value rather than a rounded number close to a boundary.

How to Use a BMI Calculator in kg and cm

Measure or check the two inputs before calculating. A scale provides weight in kilograms; a height measurement should be in centimeters. If you have measurements in other units, convert them first or use a calculator designed for those units.

• Weigh yourself without shoes and in light clothing if you want a consistent measurement.
• Measure height standing upright, without shoes, using a flat surface and a suitable measuring tool.
• Enter height as centimeters: for example, 1.70 m is 170 cm, not 1.70 cm.
• Enter weight as kilograms. If your scale shows pounds, convert pounds to kilograms by dividing by 2.20462.
• Read the result as a screening measure, not a complete description of health or body composition.

For example, someone who weighs 82 kg and is 180 cm tall has a BMI of 82 ÷ 1.8², or about 25.3 kg/m². Small changes in height or weight can shift the result, so using realistic, reasonably accurate measurements matters more than reporting many decimal places.

Adult BMI Categories and How to Read Them

For adults, commonly used World Health Organization BMI categories classify a result below 18.5 as underweight, 18.5 to below 25 as normal weight, 25 to below 30 as overweight, and 30 or above as obesity. These are broad population-level categories. A BMI of 24.9 and one of 25.0 are not meaningfully different health states, even though they fall on opposite sides of a category line.

BMI is a screening tool: it can help flag a weight range that may deserve a closer look, but it does not measure body fat directly or establish a diagnosis. A clinician may interpret it alongside other information such as medical history, physical examination, and relevant measurements. Avoid treating a category label as a verdict about an individual.

What BMI Can and Cannot Tell You

BMI is popular because it is simple to calculate and allows a consistent comparison using height and weight. It does not distinguish fat mass from muscle, bone, or other body tissue, nor does it show where fat is distributed. As a result, a muscular adult may have a higher BMI without having the same body-fat pattern as another person with the same BMI.

Age and life stage also matter. Adult BMI categories are not interpreted the same way for children and teenagers; their assessment generally uses age- and sex-specific growth charts. BMI is also not a standalone assessment during pregnancy. Older adults and people with unusual body composition may need individualized interpretation. If a result concerns you, a qualified health professional can put it in context rather than relying on the number alone.

Common Input and Interpretation Mistakes

• Using meters in a centimeters field: entering 1.70 instead of 170 makes the calculated BMI wildly too high. Convert 1.70 m to 170 cm first.
• Using pounds as kilograms: a weight of 154 lb is about 69.9 kg. Entering 154 as kg produces an incorrect result.
• Squaring the wrong height: the denominator is height multiplied by itself, not height multiplied by two.
• Rounding measurements too soon: calculate with the measured values, then round the final BMI. Rounding height or weight aggressively can change the result.
• Assuming BMI measures body fat: it is calculated from weight and height alone and cannot identify body composition.

A useful check is whether the result seems plausible for the inputs. For an adult, a typical-looking height entered in centimeters should generally be a number in the hundreds; a weight entered in kilograms is usually a number that corresponds to the scale reading after any unit conversion.

Frequently Asked Questions

How do I calculate BMI with kg and cm?
Divide weight in kilograms by height in meters squared. With height in centimeters, use BMI = weight in kg ÷ (height in cm ÷ 100)².

What is the BMI for 70 kg and 170 cm?
Convert 170 cm to 1.70 m, then calculate 70 ÷ 1.70². The result is about 24.2 kg/m².

What is a normal BMI for adults?
The commonly used adult “normal weight” BMI range is 18.5 to below 25. It is a screening category, not a guarantee of health or a personalized target.

Can I use this calculator for a child?
The arithmetic can produce a number, but adult category cutoffs are not appropriate for children and teenagers. Their BMI is usually interpreted using age- and sex-specific growth charts by a health professional.

Does BMI tell me how much body fat I have?
No. BMI uses height and weight and does not separate fat from muscle or measure fat distribution. It can be one screening measure, but it is not a direct body-fat measurement.

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in weight | Weight | kg | 70 | 0
in height | Height | cm | 170 | 0
out bmi | Body mass index | kg/m² | weight / ((height / 100) ^ 2) | 1