BMI
Calculator
Body Mass Index · Health Reference Tool
“Note: This calculator is for adults (18+). It provides an estimate of BMI and should not replace professional medical advice. For children and teens, please consult a pediatrician.”
How to Use This BMI Calculator
Enter your height and weight in either imperial (feet/pounds) or metric (cm/kg). Our BMI calculator instantly shows your Body Mass Index score and which category it falls in, along with a clear explanation of what that means for your health.
What is BMI?
Body Mass Index (BMI) is a number calculated from your height and weight, widely used by doctors as a quick screening tool to classify weight status. BMI does not directly measure body fat, but it correlates well with body fat measurements in most adults and is free, fast, and requires no special equipment.
BMI Formula
Imperial: BMI = (Weight in lbs x 703) / (Height in inches)²
Metric: BMI = Weight in kg / (Height in meters)²
BMI Categories (Adults Age 20+)
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Nutritional deficiency, osteoporosis |
| 18.5 – 24.9 | Normal / Healthy Weight | Low risk |
| 25.0 – 29.9 | Overweight | Moderate risk |
| 30.0 – 34.9 | Obese Class I | High risk |
| 35.0 – 39.9 | Obese Class II | Very high risk |
| 40.0+ | Obese Class III | Extremely high risk |
Healthy Weight Range by Height
| Height | Underweight (below 18.5) | Healthy (18.5–24.9) | Overweight (25–29.9) | Obese (30+) |
|---|---|---|---|---|
| 5’2″ | Under 101 lbs | 101–136 lbs | 137–163 lbs | 164+ lbs |
| 5’5″ | Under 114 lbs | 114–149 lbs | 150–179 lbs | 180+ lbs |
| 5’8″ | Under 125 lbs | 125–164 lbs | 164–196 lbs | 197+ lbs |
| 5’10” | Under 132 lbs | 132–173 lbs | 174–208 lbs | 209+ lbs |
| 6’0″ | Under 140 lbs | 140–183 lbs | 184–220 lbs | 221+ lbs |
Limitations of BMI
BMI is useful but imperfect. Highly muscular athletes may show a high BMI despite very low body fat. It also doesn’t differentiate between dangerous visceral fat and less-harmful subcutaneous fat. Age, sex, and ethnicity affect how BMI relates to actual health. Use BMI alongside waist circumference, blood pressure, and a doctor’s assessment for a full picture.
Tips to Improve Your BMI
- Calorie deficit: Reducing 500 calories/day leads to about 1 lb loss per week
- Strength training: Builds muscle, boosts metabolism
- 150 min cardio weekly: CDC-recommended for health maintenance
- Whole foods diet: Vegetables, lean protein, whole grains
- 7–9 hours sleep: Poor sleep increases hunger hormones
Related tools:Noom personalized weight plan → | Track calories free with MyFitnessPal →
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Frequently Asked Questions
BMI works reasonably well for most adults but overestimates body fat in muscular people and underestimates it in older adults with muscle loss. For children, age- and sex-specific BMI percentiles are used rather than the adult categories above.
The same 18.5–24.9 healthy range applies to both sexes. Women naturally carry more essential body fat than men, but the same thresholds are used clinically since both men and women with BMIs in the healthy range show similar health risk profiles.
A safe rate is 0.5–2 lbs per week through diet and exercise. Losing 10 lbs reduces BMI by roughly 1.5–2 points depending on height. Sustainable lifestyle changes beat crash diets every time for long-term BMI improvement.
A BMI below 17.5 indicates severe undernutrition. A BMI of 40 or above significantly raises risk of diabetes, heart disease, sleep apnea, and certain cancers. Consult a doctor if your BMI falls outside the 18.5–29.9 range.
This tool uses adult standards. Children aged 2–19 need age- and sex-specific growth chart percentiles from the CDC. Use the CDC’s dedicated child BMI calculator for accurate pediatric results.