How to Calculate BMI in Pounds and Inches 2026
Quick Take
BMI in US units equals your weight in pounds times 703, divided by your height in inches squared. The 703 constant converts imperial measurements into the metric-equivalent BMI formula. This guide walks through every step so you can calculate your own BMI accurately at home.
Body Mass Index, or BMI, is the most widely used weight-for-height screening tool in the United States. Doctors check it at annual physicals, insurance companies factor it into policy decisions, and millions of Americans look up their number online every single day. If you are reading this, chances are you want to understand exactly how that number gets calculated when you are used to measuring in pounds and inches rather than kilograms and meters.
The formula itself is simple once you know the constant. The confusion comes from trying to remember whether you multiply or divide, and what that 703 number actually does. This guide breaks down the calculation step by step, shows worked examples for common heights, explains what each category means, and helps you interpret your result correctly. Let's dive in.
Prefer to skip the math and get your number instantly? Use our BMI Calculator — it accepts pounds and inches directly, computes your BMI in real time, and shows which CDC category your result falls into. You can also check the Standard Weight Chart to see what weight ranges correspond to different BMI values at your height.
The Imperial Formula Explained
The standard BMI formula used across the United States and any country that relies on imperial measurements is straightforward:
BMI = (Weight in Pounds × 703) / (Height in Inches)²
That is the entire formula. Three inputs, one multiplication, one division, and you have your BMI. But where does that 703 come from, and why do we need it at all?
Why 703?
BMI was originally designed using the metric system, where the formula is simply weight in kilograms divided by height in meters squared. To convert this to imperial units, we need to account for two conversions:
First, convert pounds to kilograms: 1 pound equals approximately 0.4536 kilograms. Second, convert inches to meters: 1 inch equals approximately 0.0254 meters. Since the height is squared in the formula, we square the inch-to-meter conversion factor as well.
Doing the math: 0.4536 ÷ (0.0254)² = 0.4536 ÷ 0.00064516 = 702.94, which rounds to 703. That constant handles both conversions in one step, giving you the same BMI result as if you had converted to metric units first and used the original formula.
Step-by-Step Calculation
Here is exactly how to calculate your BMI at home using a bathroom scale and a tape measure:
Step 1: Weigh yourself in pounds. For the most accurate result, weigh yourself first thing in the morning after using the bathroom and before eating or drinking. Wear minimal clothing.
Step 2: Measure your height in inches. Stand with your back against a wall, heels together, and mark the wall at the top of your head. Measure the distance from the floor to the mark. One foot equals 12 inches, so if you are 5 feet 10 inches, that is 70 inches total.
Step 3: Multiply your weight by 703.
Step 4: Square your height in inches (multiply it by itself).
Step 5: Divide the result from Step 3 by the result from Step 4. That is your BMI.
Worked Examples
Let's work through a few real examples so you can see exactly how the math plays out for different body types.
Example 1: Average Adult
A 35-year-old person is 5'8" (68 inches) and weighs 165 pounds.
Step 1: 165 × 703 = 116,195
Step 2: 68 × 68 = 4,624
Step 3: 116,195 ÷ 4,624 = 25.13
BMI ≈ 25.1, which falls into the overweight category (25.0–29.9) per CDC standards.
Example 2: Active Individual
A 28-year-old runner is 5'10" (70 inches) and weighs 155 pounds.
Step 1: 155 × 703 = 108,965
Step 2: 70 × 70 = 4,900
Step 3: 108,965 ÷ 4,900 = 22.24
BMI ≈ 22.2, solidly in the normal range (18.5–24.9).
Example 3: Strength Athlete
A 42-year-old weightlifter is 6'0" (72 inches) and weighs 240 pounds.
Step 1: 240 × 703 = 168,720
Step 2: 72 × 72 = 5,184
Step 3: 168,720 ÷ 5,184 = 32.55
BMI ≈ 32.6, which falls into obese Class I (30.0–34.9). However, this person likely has significant lean muscle mass, making the BMI number an incomplete picture of their actual body composition.
2026 CDC BMI Classification Categories
The CDC and NIH use the same BMI categories for all adults aged 20 and older. These categories have not changed in 2026 — they remain the same WHO-based thresholds adopted by US health authorities in the late 1990s.
| Category | BMI Range | What It Means |
|---|---|---|
| Underweight | Below 18.5 | May indicate insufficient caloric intake; further assessment recommended |
| Normal | 18.5 – 24.9 | Associated with lowest mortality risk in epidemiological studies |
| Overweight | 25.0 – 29.9 | Elevated risk for hypertension, type 2 diabetes, cardiovascular disease |
| Obese Class I | 30.0 – 34.9 | High risk for metabolic conditions; medical assessment suggested |
| Obese Class II | 35.0 – 39.9 | Very high health risk; comprehensive evaluation recommended |
| Obese Class III | 40.0 and above | Highest risk level; requires thorough medical assessment |
BMI by Height and Weight: Quick Reference Table
If you prefer looking up your BMI rather than calculating it, the table below shows BMI values for common height and weight combinations. This is a quick-reference tool, not a substitute for the full calculation.
| Height | 120 lbs | 150 lbs | 180 lbs | 210 lbs | 240 lbs |
|---|---|---|---|---|---|
| 5'4" (64 in) | 20.6 | 25.7 | 30.8 | 35.9 | 41.0 |
| 5'6" (66 in) | 19.4 | 24.2 | 29.1 | 33.9 | 38.7 |
| 5'8" (68 in) | 18.4 | 23.0 | 27.6 | 32.2 | 36.8 |
| 5'10" (70 in) | 17.5 | 21.7 | 26.1 | 30.4 | 34.8 |
| 6'0" (72 in) | 16.6 | 20.7 | 24.9 | 29.0 | 33.2 |
| 6'2" (74 in) | 15.8 | 19.6 | 23.5 | 27.4 | 31.3 |
Important Limitations to Keep in Mind
BMI is a useful screening tool, but it has well-documented limitations. It cannot distinguish between muscle mass and body fat, which means athletes and weightlifters may register as "overweight" or "obese" despite having low body fat percentages. Similarly, older adults with reduced muscle mass may have "normal" BMI values while carrying excess body fat.
For a more complete picture of your body composition, consider using the Body Fat Calculator which uses the US Navy circumference method for estimating body fat percentage. The Waist-to-Height Ratio Calculator provides additional insight into fat distribution, particularly abdominal fat, which is more closely linked to metabolic health risks than total body weight alone.
The CDC explicitly states that BMI is a screening tool, not a diagnostic tool. If your BMI falls outside the normal range, or if you have other risk factors such as high blood pressure, cholesterol issues, or a family history of diabetes, consider discussing your results with a healthcare provider who can order more comprehensive assessments.