Skip to main content
AtoolinBMI Calculator
中

BMI Calculator

Enter your height and weight to calculate your Body Mass Index and see your BMI category.

--
Enter your details above

BMI is a screening tool, not a diagnostic measure. Consult a healthcare provider for a complete health assessment. Source: WHO / CDC

How Does BMI Calculator Work?

BMI uses one of two formulas depending on your unit system. Metric mode divides weight in kilograms by height in meters squared (kg/m²). Imperial mode multiplies weight in pounds by 703, then divides by height in inches squared; both arrive at the same number. The WHO set these classification thresholds in the 1990s and they remain the global standard for adult BMI. In our testing, entering 70 kg at 175 cm returns a BMI of exactly 22.86, which matches the manual calculation and lands in the normal-weight range of 18.5–24.9. No button click needed; the result updates as you type.

Why Use BMI Calculator?

A BMI check covers more ground than most people use it for. Fitness enthusiasts run it before a training program and again at the end to measure change. People prepping for a routine checkup can self-screen before the appointment; the CDC treats BMI as a low-cost first-line screening tool for adults. Athletes track body composition between seasons by pairing BMI with skinfold measurements. Insurance forms, visa medical questionnaires, and HR wellness programs often ask for BMI directly. Atoolin's bmi calculator handles metric and imperial on the same screen, so there's no tab-switching or separate unit conversion needed.

What Is a Healthy BMI Range for Adults?

A healthy BMI for adults is 18.5 to 24.9, per the World Health Organization. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above falls into one of three obesity classes. These thresholds apply to adults 18 and over regardless of sex.

BMI is a population screening metric, not a diagnosis. A strength athlete with dense muscle mass can read as overweight while carrying little actual fat. The American Heart Association recommends pairing BMI with waist circumference and other clinical markers for a fuller assessment. In our testing, a person at 178 cm (5'10") hits the healthy weight boundary between roughly 59 and 78 kg (129–173 lb), a range the calculator shows directly below your BMI result.

Frequently Asked Questions

Does BMI change with age for adults?
The formula doesn't change for adults over 18: weight divided by height squared, at 30 or at 65. Older adults tend to carry more body fat at the same BMI than younger adults, and some clinicians apply relaxed thresholds after age 65. Your doctor can put your specific score in context.
Can I have a normal BMI and still be unhealthy?
Yes. BMI reflects weight relative to height, not body fat percentage or where that fat sits. A BMI of 23 can coexist with elevated visceral fat, high blood pressure, or poor metabolic markers. A heavily muscular person at BMI 27 may be metabolically fine. BMI is a first screen, not the whole picture.
How accurate is BMI for women?
The formula is the same for men and women, but women typically carry more body fat at the same BMI value than men of the same age. A woman at BMI 24 generally has a higher fat percentage than a man at BMI 24. Research shows BMI still correlates with cardiovascular risk in women at a population level, so it works as a starting point.
What BMI is considered obese?
A BMI of 30 or above meets the WHO and CDC definition of obese. It splits into three classes: Class I (30–34.9), Class II (35–39.9), and Class III (40 and above). Class III carries substantially higher risk for type 2 diabetes, heart disease, and sleep apnea. The bmi calculator labels your category automatically after you enter your height and weight.

All processing happens in your browser. No data is sent to any server.

Related Tools

Age CalculatorCalculate your exact age with birthday countdown and milestonesPercentage CalculatorCalculate percentages, percentage change, and discounts instantly