Body mass index, or BMI, is the shorthand your doctor uses to gauge whether your weight is putting you at risk for disease. It is a quick snapshot. It strips away the noise of daily fluctuations and looks at two hard numbers: your bare weight and your height without shoes.
Calculating it yourself is straightforward if you are comfortable with math. You take your weight in pounds. You divide it by the square of your height in inches. Then you multiply that result by 703. The final number is your BMI.
Most people skip the math. They just look up a chart.
Reading the BMI Chart
If the formula feels like a chore, use the standard lookup table instead. Locate your height in inches on the vertical axis. Find your weight in pounds on the horizontal or corresponding row. The intersection point gives you your index.
Here is how to navigate that data without doing algebra.
| Height (inches) | Weight 91-167 lbs | Weight 168-179 lbs | Weight 180-197 lbs | Weight 198-216 lbs | Weight 217-236 lbs | Weight 237-258 lbs | Weight 259-287 lbs |
|---|---|---|---|---|---|---|---|
| 5’8″ (68″) | 125-164 lbs | 171-184 lbs | 190-203 lbs | 210-223 lbs | 230-243 lbs | 249-265 lbs | 272-287 lbs |
| 5’9″ (69″) | 128-169 lbs | 176-189 lbs | 196-209 lbs | 216-230 lbs | 236-250 lbs | 256-272 lbs | 279-295 lbs |
| 5’10” (70″) | 132-174 lbs | 181-195 lbs | 202-216 lbs | 222-236 lbs | 243-257 lbs | 264-279 lbs | 286-301 lbs |
| 5’11” (71″) | 136-179 lbs | 186-200 lbs | 208-222 lbs | 229-243 lbs | 250-264 lbs | 271-285 lbs | 292-307 lbs |
| 6’0″ (72″) | 140-184 lbs | 191-206 lbs | 213-228 lbs | 235-250 lbs | 257-272 lbs | 279-294 lbs | 301-316 lbs |
A BMI of 18.5 to 24.9 indicates a healthy weight with low risk for health problems.
Defining a Healthy BMI Range
The National Heart, Lung, and Blood Institute sets the baseline. A score between 18.5 and 24.9 places you in a low-risk category. This is widely considered healthy.
A score from 25 to 29.9 moves you into the overweight zone. It is a moderate risk factor.
Once you hit 30 or higher, the designation shifts to obese. This is a high-risk category for developing chronic conditions.
These guidelines are not universal laws. They are statistical averages. They fail for pregnant women. They fail for bodybuilders with high muscle mass. They may also misrepresent the elderly, whose body composition changes with age. If your situation is non-standard, ask your doctor. Do not assume the chart applies to your specific physiology.
Calculating Weight Loss Targets
A BMI of 25 or higher suggests you can lower your health risks by losing weight. You do not need to reach an “ideal” number to see benefits. Dropping just 5% to 10% of your body weight creates a significant impact on metabolic health.
The exact amount of weight to lose to drop below a BMI of 25 depends entirely on your height.
Consider someone who is 5 feet 5 inches tall.
If their current BMI is 27, they need to lose 13 pounds to fall under the 25 threshold.
If their BMI is 30, they need to lose 31 pounds to get there.
Now look at someone who is 6 feet tall.
A BMI of 27 requires losing 16 pounds to reach the healthy range.
A BMI of 30 requires a 38-pound loss.
The math scales with height. Taller individuals need to lose more absolute weight to achieve the same index score. This is
