BMI Calculator
Calculate Body Mass Index in kg/lbs and cm/ft with a healthy-range readout.
Written by Golam Rabbani, Founder & Lead Engineer — Last updated 2026-05-01
How to use this bmi calculator
- Enter your weight and select kg or lbs using the unit toggle.
- Enter your height and select cm or ft using the unit toggle.
- For feet, fill in both the Feet and Inches fields.
- Press Calculate to see your BMI value and category.
- Use Copy to save the result, or Reset to clear all fields.
About this bmi calculator
The bmi calculator takes your weight and height and returns your Body Mass Index — a single number that places you into one of four standard WHO categories: Underweight, Normal, Overweight, or Obese.
The formula is BMI = weight (kg) ÷ height (m)². The tool converts lbs to kilograms (× 0.453592) and feet/inches to metres before applying the formula, so you can work in whichever units you prefer. The result is rounded to one decimal place and a colour-coded progress bar maps it against the four category bands. This is an estimate for general information and is not a substitute for advice from a qualified clinician.
For example, a person weighing 70 kg at 175 cm has a BMI of 70 ÷ (1.75)² = 70 ÷ 3.0625 ≈ 22.9, which falls in the Normal category. The tool is useful for quick self-screening, tracking weight changes over time, or preparing for a health check-up.
FAQ
- What does a bmi calculator measure?
- It calculates Body Mass Index — a ratio of weight to height squared. The result is mapped to the standard WHO categories (Underweight, Normal, Overweight, Obese) to give a rough indication of whether body weight is in a healthy range for a given height.
- What formula does the BMI calculator use?
- BMI = weight in kilograms ÷ (height in metres)². If you enter lbs or feet/inches, the tool converts to metric first before applying the formula.
- How accurate is the BMI result?
- BMI is a population-level screening tool, not a precise measure of body fat. It can misclassify very muscular people as overweight and may be less reliable for older adults. Use it as a general guide and consult a clinician for a full assessment.
- What happens if I enter only feet without inches?
- The inches field defaults to zero, so entering 5 feet with nothing in the inches box is treated as exactly 5 ft 0 in (152.4 cm). Fill in inches as well if your height includes a fractional foot.
- Does this tool store my weight or height data?
- No. The BMI calculator runs entirely in your browser; no data is sent to a server or saved between visits. Closing the page clears all inputs.
- Is the BMI calculator free to use?
- Yes. It is completely free with no account, no signup, and no usage limit.