BMI Calculator
Calculate Body Mass Index from height and weight (metric or imperial) with WHO category ranges.
BMI is a general screening indicator, not a diagnosis. It does not account for muscle mass, body composition, age, or ethnicity, and it is not appropriate for children, athletes, or pregnancy. For any health decision, speak to a qualified healthcare professional.
Frequently Asked Questions
Is BMI an accurate measure of health?
No. BMI is a general population screening indicator, not a diagnosis. It does not distinguish muscle from fat and is less accurate for athletes, older adults, children and different ethnic groups. For any health decision, consult a qualified professional.
How is BMI calculated?
Weight in kilograms divided by height in metres squared. Imperial inputs are converted to the same formula. The WHO categories are: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese.
Is this medical advice?
No. This tool is informational only and is not a substitute for professional medical advice, diagnosis, or treatment.
Is my data sent to a server?
No. This tool runs entirely in your browser using JavaScript — nothing you enter is uploaded or stored.
The BMI Calculator computes Body Mass Index — a simple ratio of weight to height — in either metric or imperial units, and shows which standard World Health Organization category the result falls into. BMI is a widely-used population screening indicator, and this tool computes it accurately, while being clear about what BMI can and cannot tell you.
How to Use This Tool
Choose Metric or Imperial. For metric, enter height in centimetres and weight in kilograms. For imperial, enter height in feet and inches and weight in pounds. The tool shows your BMI value and its WHO category.
What This Tool Checks
The standard formula: weight (kg) ÷ height (m)², with an equivalent conversion applied to imperial inputs. The result is placed into the WHO ranges: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30 and above obese.
Understanding Your Results
BMI is a rough screening number for populations, not a diagnosis for an individual. It does not distinguish muscle from fat, does not account for where weight is carried, and is known to be less accurate for athletes, older adults, and different ethnic groups. Treat a result as a prompt for a conversation with a professional, not a verdict.
How to Fix Common Problems
If the number looks wrong, check you selected the matching unit tab for your inputs (metric height in cm, not metres). Imperial height needs both feet and inches.
SEO Best Practices
Use BMI only as one general indicator among many. For any decision about health, weight, or fitness, consult a qualified healthcare professional who can consider the full picture — this tool is informational and is not medical advice.
Example
A person 175 cm tall weighing 70 kg has a BMI of about 22.9, which falls in the WHO "normal" range. The same person in imperial units (5 ft 9 in, about 154 lb) returns the same value.
Common Mistakes to Avoid
Treating BMI as a precise measure of health or body fat. Applying adult BMI categories to children, athletes, or during pregnancy, where they do not apply.
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