What is the body mass index (BMI)?
The body mass index (BMI) is a now the measurement of choice for many physicians and researchers studying obesity.
The BMI uses a mathematical formula that accounts for both a person's weight and height.
The BMI measurement, however, poses some of the same problems as the weight-for-height tables. Not everyone agrees on the cutoff points for "healthy" versus "unhealthy" BMI ranges. BMI also does not provide information on a person's percentage of body fat. However, like the weight-for-height table, BMI is a useful general guideline and is a good estimator of body fat for most adults 19 and 70 years of age. However, it may not be an accurate measurement of body fat for body builders, certain athletes, and pregnant women.
The BMI equals a person's weight in kilograms divided by height in meters squared (BMI = kg/m2). To calculate the BMI using pounds, divide the weight in pounds by the height in inches squared and multiply the result by 703.
It is important to understand what "healthy weight" means. Healthy weight is defined as a body mass index (BMI) equal to or greater than 19 and less than 25 among all people 20 years of age or over. Generally, obesity is defined as a body mass index (BMI) equal to or greater than 30, which approximates 30 pounds of excess weight. Excess weight also places people at risk of developing serious health problems.
The World Health Organization uses a classification system using the BMI to define overweight and obesity.
- A BMI of 25 to 29.9 is defined as a "pre-obese."
- A BMI of 30 to 34.99 is defined as "obese class I."
- A BMI of 35 to 39.99 is defined as "obese class II."
- A BMI of or greater than 40.00 is defined as "obese class III."
The table below has already done the math and metric conversions. To use the table, find the appropriate height in the left-hand column. Move across the row to the given weight. The number at the top of the column is the BMI for that height and weight.
BMI (kg/m2) | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 35 | 40 |
Height (in.) | Weight (lb.) |
58 | 91 | 96 | 100 | 105 | 110 | 115 | 119 | 124 | 129 | 134 | 138 | 143 | 167 | 191 |
59 | 94 | 99 | 104 | 109 | 114 | 119 | 124 | 128 | 133 | 138 | 143 | 148 | 173 | 198 |
60 | 97 | 102 | 107 | 112 | 118 | 123 | 128 | 133 | 138 | 143 | 148 | 153 | 179 | 204 |
61 | 100 | 106 | 111 | 116 | 122 | 127 | 132 | 137 | 143 | 148 | 153 | 158 | 185 | 211 |
62 | 104 | 109 | 115 | 120 | 126 | 131 | 136 | 142 | 147 | 153 | 158 | 164 | 191 | 218 |
63 | 107 | 113 | 118 | 124 | 130 | 135 | 141 | 146 | 152 | 158 | 163 | 169 | 197 | 225 |
64 | 110 | 116 | 122 | 128 | 134 | 140 | 145 | 151 | 157 | 163 | 169 | 174 | 204 | 232 |
65 | 114 | 120 | 126 | 132 | 138 | 144 | 150 | 156 | 162 | 168 | 174 | 180 | 210 | 240 |
66 | 118 | 124 | 130 | 136 | 142 | 148 | 155 | 161 | 167 | 173 | 179 | 186 | 216 | 247 |
67 | 121 | 127 | 134 | 140 | 146 | 153 | 159 | 166 | 172 | 178 | 185 | 191 | 223 | 255 |
68 | 125 | 131 | 138 | 144 | 151 | 158 | 164 | 171 | 177 | 184 | 190 | 197 | 230 | 262 |
69 | 128 | 135 | 142 | 149 | 155 | 162 | 169 | 176 | 182 | 189 | 196 | 203 | 236 | 270 |
70 | 132 | 139 | 146 | 153 | 160 | 167 | 174 | 181 | 188 | 195 | 202 | 207 | 243 | 278 |
71 | 136 | 143 | 150 | 157 | 165 | 172 | 179 | 186 | 193 | 200 | 208 | 215 | 250 | 286 |
72 | 140 | 147 | 154 | 162 | 169 | 177 | 184 | 191 | 199 | 206 | 213 | 221 | 258 | 294 |
73 | 144 | 151 | 159 | 166 | 174 | 182 | 189 | 197 | 204 | 212 | 219 | 227 | 265 | 302 |
74 | 148 | 155 | 163 | 171 | 179 | 186 | 194 | 202 | 210 | 218 | 225 | 233 | 272 | 311 |
75 | 152 | 160 | 168 | 176 | 184 | 192 | 200 | 208 | 216 | 224 | 232 | 240 | 279 | 319 |
76 | 156 | 164 | 172 | 180 | 189 | 197 | 205 | 213 | 221 | 230 | 238 | 246 | 287 | 328 |
Table Courtesy of the National Institutes of Health
Below is a table identifying the risk of associated disease according to BMI and waist size.
Disease Risk* Relative to Normal Weight and Waist Circumference |
| BMI (kg/m2) | Obesity Class | Men 102cm (40 in) or less Women 88cm (35 in) or less | Men > 102cm (40 in) Women > 88cm (35 in) |
Underweight | < 18.5 | | | |
Normal weight | 18.5 - 24.9 | | | |
Overweight | 25.0 - 29.9 | | Increased | High |
Obesity | 30.0 - 34.9 | I | High | Very High |
Obesity | 35.0 - 39.9 | II | Very High | Very High |
Extreme Obesity | 40.0 + | III | Extremely High | Extremely High |
* Disease risk for type 2 diabetes, hypertension, and CVD.