Overview
This BMI calculator uses the standard body mass index formula to turn height and weight into one comparable number. It is useful when you want to check a recorded figure, repeat a measurement later, or keep a consistent personal record. BMI is a screening measure, not a diagnosis. It does not separate muscle, fat, bone, or body water, so the number should be read together with body build and the situation in which the measurement was taken. For a meaningful result, keep the unit system consistent and enter measured values rather than estimates. If the figure looks off, the most common reason is a unit mix-up, such as pounds entered where kilograms were expected or feet and inches used instead of centimeters.
Use cases
- Log a weigh-inAttach BMI to a dated weighing from a checkup, training log, or personal record.
- Compare two datesCalculate BMI on different dates to see how the value changed after diet, training, or time off.
- Check a published figureRecompute BMI from stated height and weight to confirm a number in a profile or report.
How it works
- 1
Choose the unit system that matches your measurements.
- 2
Enter height and weight in the same system.
- 3
Read the BMI value and the displayed category.
- 4
If the result looks wrong, check the units and enter the values again.
Examples
Metric adult example
Input: Height: 175 cm, Weight: 70 kg
Output: BMI = 22.9
A straightforward metric calculation that lands in the middle range.
Same height, higher weight
Input: Height: 160 cm, Weight: 82 kg
Output: BMI = 32.0
Shows how BMI rises when weight increases at the same height.
Tall and light frame
Input: Height: 182 cm, Weight: 66 kg
Output: BMI = 19.9
A leaner build that produces a lower value from the same formula.
FAQ
Which units should I use for height and weight?
Use one system consistently: kilograms with centimeters, or pounds with inches. Mixing systems gives the wrong result.
Why is the BMI shown with one decimal place?
One decimal place is enough for comparison and avoids implying more precision than the formula supports.
Can I enter height in feet and inches?
Only if the tool explicitly supports that format. Otherwise, convert the height to the expected unit before entering it.
Why can BMI be misleading for very muscular people?
BMI uses only height and weight, so it cannot tell whether the mass comes from muscle, fat, bone, or fluid.
What input mistake causes the biggest errors?
The biggest errors usually come from using the wrong unit in one field, such as pounds instead of kilograms or inches instead of centimeters.