Most BMI calculators online default to metric — kilograms and centimetres. If you work in pounds and inches, you end up doing a mental unit conversion before you even start, which defeats the purpose of a quick calculation tool.
This guide covers the imperial BMI formula, how to calculate it manually, and how to use a free browser-based BMI Calculator that handles imperial units natively — no conversion needed.
The Imperial BMI Formula
BMI in imperial units uses a slightly different formula from metric:
BMI = (weight in lbs × 703) ÷ (height in inches)²
The 703 factor is the unit conversion constant (kg/m² to lb/in²). Without it, you would get a number in the wrong unit system.
Step-by-step example — 165 lbs, 5'10":
- Convert height to inches: 5 × 12 + 10 = 70 inches
- Square the height: 70 × 70 = 4900
- Multiply weight by 703: 165 × 703 = 115,995
- Divide: 115,995 ÷ 4900 = 23.7
BMI of 23.7 falls in the Normal weight range (18.5–24.9).
BMI Classification (WHO Standard)
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese (Class I) |
| 35.0 – 39.9 | Obese (Class II) |
| 40.0+ | Obese (Class III) |
Quick Reference — Common Heights and Weights (Imperial)
| Weight | 5'4" | 5'6" | 5'8" | 5'10" | 6'0" | 6'2" |
|---|---|---|---|---|---|---|
| 130 lb | 22.3 N | 21.0 N | 19.8 N | 18.7 N | 17.6 U | 16.7 U |
| 150 lb | 25.8 O | 24.2 N | 22.8 N | 21.5 N | 20.4 N | 19.2 N |
| 165 lb | 28.3 O | 26.7 O | 25.1 O | 23.7 N | 22.4 N | 21.2 N |
| 180 lb | 30.9 OB | 29.1 O | 27.4 O | 25.8 O | 24.5 N | 23.1 N |
| 200 lb | 34.3 OB | 32.3 OB | 30.4 OB | 28.7 O | 27.2 O | 25.7 O |
| 220 lb | 37.8 OB | 35.5 OB | 33.5 OB | 31.6 OB | 29.9 O | 28.3 O |
N = Normal, O = Overweight, U = Underweight, OB = Obese
Healthy Weight Range by Height (Imperial)
For a BMI between 18.5 and 24.9:
| Height | Min Healthy Weight | Max Healthy Weight |
|---|---|---|
| 5'0" | 97 lb | 128 lb |
| 5'2" | 104 lb | 136 lb |
| 5'4" | 110 lb | 144 lb |
| 5'6" | 118 lb | 154 lb |
| 5'8" | 125 lb | 164 lb |
| 5'10" | 132 lb | 174 lb |
| 6'0" | 140 lb | 184 lb |
| 6'2" | 148 lb | 195 lb |
Calculate It Without the Math
If you don't want to run the formula manually every time, the free BMI Calculator supports both imperial and metric input:
- Select Imperial mode
- Enter your height in feet and inches (e.g. 5 ft 10 in)
- Enter your weight in pounds
- Get your BMI, category, and healthy weight range instantly
No account, no signup. The calculation runs entirely in your browser — nothing is sent to a server.
Imperial vs Metric — Same Result, Different Input
Both formulas give identical BMI values — imperial just includes the 703 conversion factor. If you ever need to cross-check:
Metric: BMI = weight (kg) ÷ height² (m)
Imperial: BMI = (weight (lbs) × 703) ÷ height² (inches)
The results are numerically identical for the same person, just expressed with different units as input.
Limitations to Know
BMI is a population-level screening tool, not an individual diagnostic. It does not account for:
- Muscle mass — athletes often show "overweight" BMI with very low body fat
- Fat distribution — visceral fat (around organs) carries more risk than subcutaneous fat
- Age and sex — the same BMI means different health risks for a 25-year-old vs a 65-year-old
- Ethnicity — Asian populations face higher metabolic risk at lower BMI values (threshold: 23 instead of 25)
Use BMI as a starting point, not a final verdict. A healthcare professional can give a complete picture.
Related Tools
Other free health and utility calculators that run in your browser:
- EMI Calculator — calculate loan EMI, compare offers, reverse EMI from monthly budget
- Unit Converter — convert lbs to kg, inches to cm, and 100+ other unit pairs
- Invoice Generator — create GST, HST, VAT, and US invoices as PDF, no account
Calculate your BMI in imperial units — lbs and inches, no conversion needed: BMI Calculator
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