Free calculator · metric & imperial
BMI Calculator
Enter your height and weight to see your Body Mass Index, what it means, and the healthy weight range for your height.
For adults aged 18 and over. BMI is a screening tool, not a medical diagnosis. Talk to a doctor about your health and weight.
Run a gym, clinic or fitness business?
Get a website that books clients for you.
I build fast websites for gyms, clinics and coaches, with online booking, calculators like this one and forms that turn visitors into clients.
BMI categories for adults
- Below 18.5: underweight
- 18.5 – 24.9: healthy weight
- 25 – 29.9: overweight
- 30 – 34.9: obese (class I)
- 35 – 39.9: obese (class II)
- 40 and above: obese (class III)
Some health organisations recommend lower thresholds for people of Asian backgrounds (overweight from 23, obese from 27.5), because health risks start at a lower BMI.
Beyond BMI
Waist size is a useful second check: a waist over about 94 cm (37 in) for men or 80 cm (31.5 in) for women suggests extra health risk, whatever your BMI. Need to convert units? Try the Unit Converter.
Frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared. For example, 70 kg at 1.75 m gives 70 ÷ (1.75 × 1.75) = 22.9. In pounds and inches the formula is 703 × weight ÷ height².
What is a healthy BMI?
For adults, the World Health Organization classes 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight and 30 or more as obese. Under 18.5 is underweight.
Is BMI accurate for everyone?
BMI is a quick screening number, not a diagnosis. It does not tell muscle from fat, so athletes can score "overweight" while being healthy, and it can underestimate risk in older adults. Some health bodies use lower cut-offs for people of South Asian, Chinese and other Asian backgrounds.
Can I use this for children?
No. Children and teenagers are assessed with BMI-for-age percentiles that depend on age and sex. Ask a doctor or use a child-specific BMI calculator.
What is BMI Prime?
BMI Prime is your BMI divided by 25, the top of the healthy range. A BMI Prime under 1.0 means you are within or below the healthy range.
More calculators
Percentage Calculator
Percent of a number, percentage change, increase or decrease, and more, with the working shown.
Age Calculator
Exact age in years, months and days, plus total days and a next-birthday countdown.
Loan & EMI Calculator
Monthly payment, total interest and a full repayment schedule for any loan or mortgage.
Date Calculator
Days between two dates, working days, and adding or subtracting days, weeks or months.
Unit Converter
Convert length, weight, temperature, volume, area, speed, time and data units instantly.
GPA & CGPA Calculator
Work out your GPA and CGPA from grades and credits, and convert between CGPA and percentage.