BMI Calculator
Calculate your BMI from height and weight in metric or imperial units. Shows the WHO weight category and where you sit in the healthy range — no signup.
Last updated: May 2026
Enter height and weight to calculate BMI.
What this calculator is for
BMI is a blunt screening tool, but it is still one of the most used body-weight checks on the web. People use it because it is fast and gives a rough starting point before they go deeper.
The number does not account for muscle mass, age, body composition or medical context. Treat it as orientation only, not as a final health judgement. If you have concerns about your weight or health, consult a healthcare professional — BMI alone is not a basis for medical decisions. For evidence-based health information, see CDC healthy weight resources.
Typical use cases
- basic weight context
- fitness tracking
- health article reference
- repeat personal checks
WHO BMI classification
BMI categories are defined by the World Health Organization (WHO). The classifications below reflect current global health standards and are the basis for most public health assessments.
| BMI range | Category | Health implication |
|---|---|---|
| Below 18.5 | Underweight | May indicate malnutrition or low body fat |
| 18.5 to 24.9 | Normal weight | Associated with lowest health risk for most adults |
| 25.0 to 29.9 | Overweight | Elevated risk for metabolic conditions |
| 30.0 to 34.9 | Obese class I | High risk; lifestyle changes typically recommended |
| 35.0 to 39.9 | Obese class II | Very high risk; medical supervision often needed |
| 40.0 and above | Obese class III | Severe risk; significant health complications likely |
Related tools and sections
Frequently Asked Questions
Why is BMI criticized by doctors and fitness professionals?
BMI measures weight-to-height ratio but ignores body composition entirely. A 6'0" 230-lb muscular athlete and a 6'0" 230-lb sedentary person get identical BMI scores (~31, "overweight"), but their health profiles are completely different. Athletes with heavy muscle mass often fall into "overweight" or even "obese" BMI ranges. BMI also doesn't account for bone density, organ density, or water retention. For these reasons, many health professionals use it only as a screening starting point, not a diagnostic tool.
Does age change how BMI should be interpreted?
Yes, significantly. Older adults lose muscle mass naturally and gain fat deposits while maintaining weight—their BMI stays the same but their actual body composition has shifted toward less healthy distribution. Conversely, younger people with athletic builds often have high BMI despite low body fat. Children and teens have different BMI categories entirely because their body composition changes with development. A BMI "normal" range (18.5–24.9) that fits a 25-year-old might not reflect health risk accurately for a 65-year-old.
What about people with naturally high bone density or large muscle mass?
They'll often be classified as overweight or obese by BMI even if they're metabolically healthy. A powerlifter or swimmer building muscle intentionally can rack up BMI scores in the 27–30 range while maintaining 12–15% body fat. BMI cannot distinguish between weight that's muscle, bone, fat, or water. If BMI flags you as overweight but you're lean or athletic, consider body-fat percentage, waist circumference, or fitness metrics like VO2 max instead. BMI is useful as a population-level screening tool, not for individuals with non-standard body composition.
Should I aim for a "normal" BMI if I'm overweight?
That depends on your starting point and health markers. BMI categories are based on population statistics and health risk correlation, not absolutes. If you have high blood pressure, high cholesterol, or poor fitness, losing weight and moving toward "normal" BMI is generally good. But if you're already healthy by other metrics (good cholesterol, normal blood pressure, good fitness), hitting an exact BMI number is less important than staying active and eating well. Always combine BMI results with actual health markers—blood work, fitness tests, and how you feel—before making changes.
Is there a better measure than BMI for personal health?
Yes, several. Body-fat percentage (via DEXA scan, underwater weighing, or calipers) directly measures what's fat vs muscle. Waist circumference correlates well with metabolic health independent of weight. Fitness tests like submaximal VO2 max predict longevity better than BMI. Labs like triglycerides, LDL, HDL, and blood glucose reveal metabolic risk that BMI completely misses. The best approach is combining multiple metrics: what does your body composition look like, how fit are you, what does your bloodwork show, and how do you feel day-to-day. BMI is one data point, not the destination.