How to use the BMI calculator
- Tap Metric or US for your units.
- Enter height and weight—the result updates instantly.
- See your BMI number, category label, position on the color chart, and the weight range that matches BMI 18.5–24.9 at your height.
BMI formula
Metric: BMI = weight (kg) ÷ height (m)². US: BMI = 703 × weight (lb) ÷ height (in)².
Example: 170 cm, 70 kg
Height 1.70 m → BMI ≈ 70 ÷ 2.89 ≈ 24.2 (often labeled normal weight for adults).
BMI is a population screening tool, not a diagnosis of body fat or health. Athletes with high muscle mass may read “overweight” despite low fat—consider the body fat calculator when you have tape measurements, or BMR / calorie tools for intake planning.
Understanding BMI categories
Adult bands commonly label under 18.5 as underweight, 18.5–24.9 as normal, 25–29.9 as overweight, and 30+ as obese. Cutoffs differ by country and guideline year—treat labels as screening text, not a diagnosis.
Example: switching units
5 ft 7 in and 154 lb in US mode should land near the same BMI as 170 cm and 70 kg in metric when conversions are consistent.
Who BMI fits poorly
Very muscular athletes, some older adults with sarcopenia, and pregnancy need different metrics. Children require age- and sex-specific charts. When you have tape measures, the body fat calculator adds a circumference-based estimate beyond BMI alone.
How do I calculate BMI with height and weight?
Pick metric (cm and kg) or US (feet, inches, pounds), enter your measurements, and read BMI on the right. Metric formula: BMI = kg ÷ (m)². US formula: BMI = 703 × lb ÷ (in)². The page calculates automatically as you type.
What is a normal BMI for adults?
Many health charts label 18.5–24.9 as normal weight, below 18.5 as underweight, 25–29.9 as overweight, and 30+ as obese. Exact wording varies by country and guideline year. This calculator shows the band and a chart marker for quick screening—not a diagnosis.
BMI for 170 cm and 70 kg—what is it?
About 24.2, usually in the normal range on adult charts. Enter 170 and 70 in metric mode to match your numbers. If you use feet and inches, 5 ft 7 in with 154 lb is a similar example.
Can I use BMI for kids or teens?
Not with adult cutoffs on this page. Children and teens need age- and sex-specific BMI percentiles from growth charts. Use pediatric tools or clinical guidance instead of adult 18.5 / 25 / 30 thresholds.
Is BMI wrong if I lift weights or have muscle?
BMI uses only height and weight, so very muscular people may land in “overweight” without excess body fat. It also does not show belly fat versus hip fat. Athletes often pair BMI with the body fat calculator, waist measure, or clinical advice. For daily calories after weight goals, use the calorie calculator (built on BMR).
170 cm height—what weight for BMI 18.5 to 24.9?
Roughly 53.5 kg to 72 kg. The calculator shows this range under the inputs when height is valid—useful for goal-setting, not medical prescribing.
Why does my BMI differ from another website?
Usually rounding (height in feet/inches, decimal places) or different category labels. Compare the raw BMI number first; small differences under 0.3 often come from input rounding.
Pregnant or postpartum—use this BMI?
No. Pregnancy weight needs obstetric guidance, not standard adult BMI bands. Postpartum timing also changes interpretation—ask your clinician.