About Health BMI Calculator

Calculate BMI with health categories, ideal weight range, and health assessment. Part of the DevTools Surf developer suite. Browse more tools in the Calculators collection.

Use Cases

• Get a quick baseline health metric as part of a personal fitness tracking routine.
• Calculate BMI for a group of patients and flag those in high-risk categories.
• Compare BMI across different height/weight combinations when researching healthy weight targets.
• Estimate the weight change needed to move from one BMI category to another.

Tips

• Enter height and weight in either metric or imperial — switch units using the toggle without re-entering values.
• Read the BMI category result alongside the ideal weight range, not just the number — context matters more than a single score.
• Use the BMI trend tracker to log weekly measurements and see progress over time.

Fun Facts

• BMI (Body Mass Index) was invented by Belgian mathematician Adolphe Quetelet in the 1830s as a population statistics tool — not a clinical health metric. Its use for individual health assessment began only in the 1970s.
• The current BMI cutoffs (overweight at 25, obese at 30) were established by the World Health Organization in 1995. Prior to that, US cutoffs placed overweight at 27.8 for men.
• BMI has a known limitation for athletic individuals: muscle is denser than fat, so elite athletes frequently score in the 'overweight' range (BMI 25-29) despite very low body fat percentages.

FAQ

Is BMI an accurate health indicator?

BMI correlates with population-level health outcomes but is imprecise for individuals. It doesn't account for muscle mass, bone density, or fat distribution. Use it as one of several indicators, not a definitive measure.

What are the BMI categories?

Underweight: <18.5, Normal: 18.5-24.9, Overweight: 25-29.9, Obese class I: 30-34.9, class II: 35-39.9, class III: 40+. WHO classifications used by default.

Does it calculate ideal body weight?

Yes — it shows the weight range corresponding to BMI 18.5-24.9 for your height, and the midpoint (BMI 22) as the commonly cited ideal.