BMI Calculator
Use this tool to estimate your body mass index and weight category.
Tip: BMI is a screening tool and not a full diagnosis of health.
What is BMI?
Body Mass Index (BMI) is a simple ratio of weight to height used to estimate whether your body weight falls within a healthy range. It is one of the most common screening tools in health care, fitness programs, and public health reporting because it is quick, inexpensive, and easy to calculate.
BMI does not directly measure body fat, muscle mass, bone density, or overall wellness. Instead, it gives a broad risk indicator. Think of it as a starting point for a conversation, not the final answer.
BMI Formula
Metric Formula
BMI = weight (kg) ÷ [height (m)]²
Example: If your weight is 70 kg and your height is 1.75 m: BMI = 70 ÷ (1.75 × 1.75) = 22.86
Imperial Formula
BMI = 703 × weight (lb) ÷ [height (in)]²
Example: If your weight is 154 lb and height is 69 in: BMI = 703 × 154 ÷ (69 × 69) ≈ 22.7
Adult BMI Categories
- Below 18.5: Underweight
- 18.5 to 24.9: Normal weight
- 25.0 to 29.9: Overweight
- 30.0 to 34.9: Obesity Class I
- 35.0 to 39.9: Obesity Class II
- 40.0 and above: Obesity Class III
How to Interpret Your BMI Result
A healthy BMI range is often associated with lower risk of chronic diseases such as type 2 diabetes, high blood pressure, heart disease, and sleep apnea. However, risk depends on many factors:
- Waist circumference
- Physical activity level
- Diet quality
- Smoking and alcohol use
- Genetics and family history
- Age and hormonal status
If your BMI falls outside the normal range, do not panic. Use it as a prompt to assess lifestyle habits and speak with a qualified clinician.
Limitations of BMI
1) It can overestimate fatness in muscular people
Athletes and strength-trained individuals may have high BMI because of lean mass, not excess fat. Their metabolic health may still be excellent.
2) It can underestimate risk in people with low muscle mass
Older adults may have a “normal” BMI but higher body fat percentages and lower muscle mass, which can still raise health risks.
3) It does not show fat distribution
Abdominal fat (around the waist) is more strongly linked to cardiometabolic risk than fat in other areas. Waist-to-height ratio and waist circumference can add useful context.
Healthy BMI Improvement Strategies
If your BMI is above your target range
- Create a modest calorie deficit (usually 300–500 kcal/day).
- Prioritize protein and high-fiber foods to improve satiety.
- Build a strength-training routine 2–4 times per week.
- Increase daily movement (walking, stairs, standing breaks).
- Sleep 7–9 hours and manage stress to support appetite control.
If your BMI is below your target range
- Increase calorie intake with nutrient-dense foods.
- Include protein at each meal and resistance training.
- Add snacks such as nuts, yogurt, smoothies, and whole grains.
- Check for medical causes if unintentional weight loss occurred.
Frequently Asked Questions
Is BMI accurate for everyone?
No. BMI is useful at population level and for initial screening, but personal health assessments should include additional measurements.
Can I use BMI for children?
Children and teens require age- and sex-specific BMI percentiles, not adult cutoffs. Pediatric growth charts are the proper reference.
How often should I check BMI?
Monthly or quarterly is usually enough for trend tracking. Daily checks are rarely useful and may create unnecessary stress.
Final Thoughts
BMI is best used as a quick snapshot, not a label. Combine your BMI with waist measurements, physical fitness, blood markers, and how you feel day to day. Sustainable habits—not short-term extremes—drive long-term health improvements.