BMI calculator
Calculate body mass index using metric or imperial inputs.
What this calculator covers
Calculate body mass index from weight and height and see how the number maps to a standard category. Choose metric (kilograms and centimeters) or imperial (pounds and inches) — the calculator converts internally so the result is identical either way.
Frequently asked questions
- What is BMI?
- Body mass index is a number derived from weight and height. BMI = weight (kg) ÷ height (m)². It is a rough screening tool for weight categories but does not directly measure body fat or overall health.
- What are the standard BMI categories?
- Underweight is below 18.5, normal is 18.5 to 24.9, overweight is 25.0 to 29.9, and obesity is 30.0 or higher. These are World Health Organization thresholds used broadly in clinical practice.
- Is BMI a reliable health indicator?
- It is a crude starting point, not a diagnosis. Athletes with high muscle mass can register as overweight despite being lean, and older adults can have healthy body composition at a higher BMI. Pair BMI with other indicators — waist circumference, body composition, blood work — for a fuller picture.
- Does this calculator support imperial units?
- Yes. Select the Imperial option to enter weight in pounds and height in inches. The calculator converts those values to kilograms and meters internally using the standard conversion factors (1 lb = 0.45359237 kg, 1 in = 2.54 cm) before running the BMI formula. The result is numerically identical to what you would get by entering the exact metric equivalents.
Tool
Run the calculation
Result
RESULT · BMI
â„–003
Primary result
24.5
BMI for 75 kg at 175 cm is 24.5, which is normal.
- Unit system
- Metric
- BMI category
- normal
- Weight used
- 75 kg
- Height used
- 1.75 m
- Unrounded BMI
- 24.4898
Step-by-step solution
- 1.Convert height from centimeters to meters: 175 cm = 1.75 m.
- 2.Square the height: 1.75 × 1.75 = 3.0625.
- 3.Divide 75 kg by 3.0625 m² and round to 1 decimal: 24.5.
Walkthrough
Visual walkthrough
BMI compares body mass with height squared so the result stays proportional across heights.
01
Convert height to meters
175 cm ÷ 100 = 1.75 m
The BMI formula uses height in meters; centimeters are divided by 100.
02
Square the height
1.75 × 1.75 = 3.0625
BMI uses height squared so taller bodies are not compared linearly to shorter ones.
03
Divide weight by height squared
75 ÷ 3.0625 = 24.4898
That ratio produces the BMI value before display rounding.
04
Interpret the category
The displayed BMI is rounded to one decimal place, but the category uses the unrounded BMI against standard adult BMI ranges.
Category normal