Table of Contents
What is BMI?
Body Mass Index (BMI) is a simple numerical measure that uses your height and weight to estimate whether you have a healthy body weight. It was developed in the early 19th century by Belgian mathematician Adolphe Quetelet.
BMI Definition: A person's weight in kilograms divided by the square of their height in meters.
BMI is widely used as a screening tool by healthcare providers because it's quick, inexpensive, and correlates reasonably well with body fat levels for most people.
How to Calculate BMI
Metric Formula
Example: 70 kg, 1.75 m = 70 ÷ 1.75² = 70 ÷ 3.06 = 22.9
Imperial Formula
Example: 154 lbs, 69 in = (154 ÷ 4761) × 703 = 22.7
Note: While the formulas are straightforward, our BMI calculator handles all the math automatically and shows your category and healthy weight range.
BMI Categories & Ranges
The World Health Organization (WHO) defines the following BMI categories for adults:
May indicate malnutrition or health issues
Lowest risk of weight-related health issues
Increased risk of health problems
High risk of health problems
Very high risk of health problems
Extremely high risk, may need medical intervention
BMI Chart by Height
Here's what a "normal" BMI (18.5-24.9) weight range looks like for various heights:
| Height | Normal Weight Range |
|---|---|
| 5'0" (152 cm) | 97-128 lbs (44-58 kg) |
| 5'3" (160 cm) | 107-141 lbs (49-64 kg) |
| 5'6" (168 cm) | 118-155 lbs (54-70 kg) |
| 5'9" (175 cm) | 128-169 lbs (58-77 kg) |
| 6'0" (183 cm) | 140-184 lbs (64-84 kg) |
| 6'3" (191 cm) | 152-200 lbs (69-91 kg) |
BMI Limitations
While BMI is useful, it has significant limitations you should understand:
Doesn't Distinguish Fat from Muscle
Athletes with high muscle mass may be classified as "overweight" despite being very healthy.
Doesn't Show Fat Distribution
Belly fat (visceral fat) is more dangerous than fat elsewhere, but BMI doesn't measure where fat is stored.
Same Scale for Everyone
Doesn't account for differences in age, gender, ethnicity, or body frame size.
Not for Children
Children and teens need age and sex-specific BMI percentiles, not adult categories.
Bottom Line: BMI is a useful screening tool, but it's not a diagnostic measure. A doctor can assess your overall health considering BMI alongside other factors.
Health Risks by BMI
Research shows correlations between BMI and various health conditions:
Underweight Risks
- • Malnutrition and vitamin deficiencies
- • Weakened immune system
- • Osteoporosis
- • Fertility issues
Overweight/Obese Risks
- • Type 2 diabetes
- • Heart disease and stroke
- • High blood pressure
- • Certain cancers
- • Sleep apnea
- • Joint problems
Beyond BMI: Other Measures
For a more complete health picture, consider these additional measurements:
Waist Circumference
Measures abdominal fat, which is more dangerous than fat elsewhere.
Target: Men under 40" (102 cm), Women under 35" (88 cm)
Waist-to-Hip Ratio
Compares waist and hip measurements to assess fat distribution.
Target: Men under 0.9, Women under 0.85
Body Fat Percentage
Directly measures the proportion of your body that is fat tissue.
Healthy range: Men 10-20%, Women 20-30%
Blood Tests
Cholesterol, blood sugar, and other markers provide important health information that BMI cannot.
Calculate Your BMI
Get your BMI, healthy weight range, and category with our free calculator!
Try BMI Calculator