BMI Calculator
Body Mass Index (BMI) is a screening measure of body fat based on height and weight. Use imperial (feet, inches, pounds) or metric units to find your BMI category and healthy weight range.
Your inputs
Your BMI
BMI categories (adults 20+)
Standard categories defined by the World Health Organization and U.S. CDC.
| BMI range | Category | What it means |
|---|---|---|
| Below 18.5 | Underweight | Possible nutrient deficiency or underlying condition. Talk to a doctor. |
| 18.5 – 24.9 | Healthy weight | Lowest disease risk for most adults age 20+. |
| 25.0 – 29.9 | Overweight | Modestly higher risk of cardiovascular and metabolic conditions. |
| 30.0 – 34.9 | Obesity (Class I) | Elevated risk; lifestyle interventions recommended. |
| 35.0 – 39.9 | Obesity (Class II) | High risk of type 2 diabetes, hypertension, sleep apnea. |
| 40.0+ | Obesity (Class III) | Very high risk; may qualify for medical or surgical intervention. |
Healthy weight ranges by height
Weight range that puts an adult in the BMI 18.5–24.9 "healthy" category. Same formula applies regardless of sex.
| Height | Healthy range (lbs) | Healthy range (kg) |
|---|---|---|
| 4'10" (147 cm) | 89 – 119 lbs | 40 – 54 kg |
| 5'0" (152 cm) | 95 – 128 lbs | 43 – 58 kg |
| 5'2" (157 cm) | 101 – 136 lbs | 46 – 62 kg |
| 5'4" (163 cm) | 108 – 145 lbs | 49 – 66 kg |
| 5'6" (168 cm) | 115 – 155 lbs | 52 – 70 kg |
| 5'8" (173 cm) | 122 – 164 lbs | 55 – 74 kg |
| 5'10" (178 cm) | 129 – 174 lbs | 59 – 79 kg |
| 6'0" (183 cm) | 137 – 184 lbs | 62 – 83 kg |
| 6'2" (188 cm) | 144 – 194 lbs | 65 – 88 kg |
| 6'4" (193 cm) | 152 – 205 lbs | 69 – 93 kg |
What is a healthy BMI by age?
The 18.5–24.9 healthy range applies to adults age 20 and older. For children and teens (ages 2–19), BMI is interpreted using CDC growth charts that compare to peers of the same age and sex (BMI percentile), not the adult categories. For older adults (65+), some research suggests that a slightly higher BMI (25–27) is associated with the lowest mortality, but recommendations still target the standard healthy range for chronic disease prevention.
- Ages 2–19: use BMI-for-age percentile (CDC growth chart) — not adult categories.
- Ages 20–64: standard adult categories apply (18.5–24.9 healthy).
- Ages 65+: standard range still applies; some studies favor 25–27 for mortality risk.
- Pregnancy: BMI is not a useful measure during pregnancy.
BMI for men vs women
The BMI formula and category cutoffs are identical for men and women — there is no separate "male BMI" or "female BMI". However, women on average carry a higher healthy body fat percentage than men at the same BMI (typically 21–35% vs. 8–24%), and men typically carry more muscle mass. This is one reason BMI alone is a limited screening tool: it doesn't distinguish between fat mass and lean mass. A muscular athlete and a sedentary person can have the same BMI but very different body composition and health profiles.
Better alongside BMI
- • Waist-to-height ratio (target < 0.5)
- • Body fat percentage (DEXA, bioimpedance)
- • Resting blood pressure, fasting glucose, lipid panel
- • Cardiovascular fitness (VO₂ max, resting heart rate)
When BMI misclassifies
- • Heavily muscled athletes (high BMI ≠ unhealthy)
- • Older adults with low muscle mass (normal BMI ≠ healthy)
- • People with edema or fluid retention
- • Different ethnic groups — Asian populations may carry higher risk at lower BMI
The BMI formula
BMI is a simple ratio of weight to height squared. The formula is the same everywhere — only the units differ:
Metric
BMI = weight (kg) ÷ height (m)²
Example: 70 kg ÷ (1.75 m)² = 70 ÷ 3.0625 ≈ 22.9 BMI
Imperial (US)
BMI = (lbs ÷ in²) × 703
Example: (160 ÷ 69²) × 703 = (160 ÷ 4,761) × 703 ≈ 23.6 BMI
Frequently asked questions
What is a healthy BMI?
The CDC defines BMI 18.5–24.9 as the 'healthy' range for adults. Below 18.5 is underweight; 25.0–29.9 is overweight; 30.0+ is obese (split into Class I 30–34.9, Class II 35–39.9, Class III 40+). These ranges apply to most adults age 20+.
Is BMI accurate?
BMI is a quick screening tool, not a diagnostic measure. It can misclassify athletes (high muscle mass = high BMI) and older adults (lower muscle, higher fat at the same BMI). Body fat percentage, waist-to-height ratio, and metabolic markers give a fuller picture of metabolic health.
Is BMI calculated differently for men and women?
No — the formula and category cutoffs are the same for men and women. However, women on average have a higher healthy body fat percentage than men at the same BMI, which is one reason BMI alone is a limited screening tool. Body composition matters more than BMI in isolation.
What's the BMI formula?
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = (weight in lbs ÷ height in inches²) × 703. Example (imperial): a 160-lb person at 5'9" (69 in) has BMI = (160 ÷ 69²) × 703 ≈ 23.6.
Does BMI work for children?
No — for ages 2–19, BMI is interpreted using CDC growth charts that compare a child's BMI to peers of the same age and sex (BMI-for-age percentile). The adult cutoffs (18.5, 25, 30) do not apply to kids and teens.
What is a healthy BMI by age for adults?
For adults age 20–64, the healthy range is 18.5–24.9. For adults 65+, the same range applies as a target for chronic disease prevention, though some studies suggest mortality risk is lowest in the 25–27 range for older adults — the evidence is mixed, so consult a clinician.
Can I have a healthy BMI and still be unhealthy?
Yes. BMI doesn't measure body composition, fitness, or metabolic health. A person can have a 'normal' BMI but high visceral fat, poor cardiovascular fitness, or metabolic markers like elevated fasting glucose ('normal-weight obesity' or 'metabolically obese normal-weight'). Conversely, very muscular people often have high BMI but excellent metabolic health.