Most BMI calculators ask you to convert your height into centimeters and your weight into kilograms before they will show you a number. That is awkward for anyone who grew up reading their height on a driver's license as 5'10" and their weight on a bathroom scale in pounds. This imperial BMI calculator skips the unit conversion entirely: type your feet, your inches, and your weight in pounds, and it returns your BMI, your NIH/WHO weight category, and the healthy weight range for your height — all in the units you already think in.
The formula underneath is the same Quetelet index used by the CDC, the WHO, and every US clinical guideline. The only difference is the constant: the imperial version multiplies by 703 so that the result lands on the familiar 18.5 / 25 / 30 cutoffs.
How to Use
- Enter your height in feet — for example, if you are 5 feet 10 inches, type 5 into the Feet box.
- Enter the remaining inches — in the same example, type 10 into the Inches box. Together these are converted to total inches (5 × 12 + 10 = 70 in) so you never have to do the math yourself.
- Type your weight in pounds into the Weight box. Use your most recent morning reading on the same scale, before eating, for consistency.
- Read the result card: your BMI number, your category (Underweight, Normal, Overweight, or Obese), and the healthy weight range for your exact height.
- If you are above the normal range, the last line tells you how many pounds you would need to lose to bring your BMI down to 25 — the upper edge of "Normal." If you are already below 25, that line shows a small negative number, which means you are on the low side and have room to move up toward the middle of the range.
The result updates instantly as you type. Try swapping the feet and inches boxes to see how a 5'9" vs 5'11" frame changes your healthy weight band by roughly ten pounds.
The Imperial BMI Formula
The metric formula is the classic one: BMI = weight in kilograms divided by height in meters squared. The imperial version folds the conversion factors (1 kg = 2.20462 lb and 1 in = 0.0254 m) into a single constant:
BMI = 703 × weight (lb) ÷ height (in)²
Worked example: a 180-lb person who is 5'10" tall. Total inches = 5 × 12 + 10 = 70. BMI = 703 × 180 ÷ 70² = 126,540 ÷ 4,900 = 25.8. That is just over the 25 threshold, which puts the result in the Overweight category — the canonical reference case for an imperial BMI calculator.
The same person on the metric scale weighs 81.6 kg and stands 1.78 m tall. BMI = 81.6 ÷ (1.78²) = 81.6 ÷ 3.168 = 25.8. The number matches to one decimal place, which is exactly why the 703 constant works.
The NIH / WHO Categories
The adult cutoffs used in the United States come from the NHLBI's 1998 Clinical Guidelines and are adopted by the CDC:
- Underweight: BMI below 18.5. Associated with higher risk of nutrient deficiency, osteoporosis, and menstrual irregularity in women.
- Normal: BMI 18.5 to 24.9. Considered the lowest range for weight-related disease risk.
- Overweight: BMI 25.0 to 29.9. Elevated risk of type 2 diabetes, hypertension, and dyslipidemia.
- Obese: BMI 30.0 and above. Further subdivided into Class I (30–34.9), Class II (35–39.9), and Class III (40+).
These cutoffs apply to adults aged 20 to 65. They do not apply the same way to children and teens, who are mapped onto age- and sex-specific percentiles (see the CDC BMI-for-age growth charts), or to competitive athletes with high muscle mass, whose BMI can read as "Overweight" despite a very low body-fat percentage.
Examples
Example 1 — The 5'10", 180-lb reference case. Feet = 5, inches = 10, weight = 180 lb. Total inches = 70. BMI = 703 × 180 ÷ 4,900 = 25.8, category Overweight. The healthy weight range for 70 inches tall is about 129–174 lb, so this person is roughly 6 lb above the upper normal limit. Losing 6 lb drops BMI to exactly 25.0.
Example 2 — A normal-weight woman. Feet = 5, inches = 4, weight = 125 lb. Total inches = 64. BMI = 703 × 125 ÷ 4,096 = 21.5, category Normal. The healthy band for 64 inches is about 107–145 lb, which puts her comfortably in the middle.
Example 3 — A 6'2" man at 240 lb. Feet = 6, inches = 2, weight = 240 lb. Total inches = 74. BMI = 703 × 240 ÷ 5,476 = 30.8, category Obese (Class I). The healthy range for 74 inches is about 152–205 lb, so reaching the upper normal limit means losing roughly 35 lb.
Example 4 — A tall athlete. Feet = 6, inches = 0, weight = 210 lb. Total inches = 72. BMI = 703 × 210 ÷ 5,184 = 28.5, category Overweight. A muscular linebacker or gymnast with this height and weight can have a body-fat percentage in the teens; BMI flags them as overweight even though their cardiometabolic risk is low. Use waist circumference (over 40 in for men, 35 in for women) as a second check.
FAQ
How do I calculate BMI in pounds and inches?
Use the formula BMI = 703 × weight in pounds ÷ (height in inches)². Convert your height to total inches first: feet × 12 + extra inches. For example, 5'8" = 5 × 12 + 8 = 68 inches. A 160-lb person who is 68 inches tall has BMI = 703 × 160 ÷ 68² = 24.4, which falls in the Normal range.
What is the 703 constant and where does it come from?
The 703 factor converts pounds-per-square-inch into the same scale as the metric BMI (kg/m²). It comes from two unit conversions: 1 inch = 0.0254 meters, so 1 in² = 0.00064516 m²; and 1 lb = 0.453592 kg. Dividing those factors gives 0.453592 ÷ 0.00064516 ≈ 703. The CDC and NIH use 703 in all their imperial BMI worksheets.
What is a healthy BMI for a 5'10" male?
For a 5'10" person (70 inches tall), the normal BMI range of 18.5 to 24.9 translates to roughly 129 to 174 pounds. BMI 25 corresponds to about 175 lb, and BMI 30 corresponds to about 210 lb. Those thresholds are the standard adult cutoffs regardless of sex.
Does BMI work for athletes and muscular people?
No, not perfectly. BMI does not distinguish muscle from fat, so a very muscular athlete can read as Overweight or Obese despite low body fat. If your BMI is over 25 but your waist circumference is below 40 in (men) or 35 in (women) and your blood pressure, blood sugar, and lipids are normal, your cardiometabolic risk is likely low even though BMI flags you.
Why does this calculator use feet and inches instead of a single height box?
Because that is how adults in the US record their height. Splitting feet and inches matches the driver's-license format and avoids the most common user error: typing "510" and expecting it to mean 5'10" rather than 510 inches. The tool does the feet × 12 + inches math for you behind the scenes.
What weight do I need to lose to reach a normal BMI?
The result card shows this directly. If your BMI is 28 at 70 inches, your weight is about 194 lb. The normal-upper weight for 70 inches is about 175 lb, so the tool reports that you need to lose roughly 19 lb to bring your BMI down to 25. Even a 5–10% weight loss significantly reduces blood pressure, triglycerides, and diabetes risk.
Is BMI different for men and women?
The BMI formula and the 18.5 / 25 / 30 cutoffs are identical for adult men and women. Sex-based differences appear in body-fat distribution (women tend to carry fat lower on the body, men around the abdomen), which is why waist circumference matters as a companion measure — but the BMI number itself does not change by sex.
Disclaimer
This imperial BMI calculator is provided for informational purposes only and is not medical advice or a substitute for a consultation with a licensed healthcare professional. Body Mass Index is a population-level screening tool, not a diagnostic one; it does not measure body fat directly, account for muscle mass, age, ethnicity, or medical history, and should not be used alone to make treatment or dietary decisions. Always discuss your weight, nutrition, and activity goals with your doctor or a registered dietitian before starting a new diet or exercise program.