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Health & Body
BMI Calculator — Body Mass Index in Pounds, Feet & Inches
A quick screening number from your height and weight — not a diagnosis
Body Mass Index (BMI) is the number your doctor, the CDC, and most fitness apps use as a fast first screen for whether your weight is in a healthy range for your height. It doesn't measure body fat directly and it isn't a diagnosis — but it's free, takes ten seconds, and is the same yardstick used in U.S. health guidelines, so it's a useful starting point.
The math is simple. With American units (pounds and inches) the formula is:
BMI = 703 × weight (lb) ÷ height (in)²
The 703 is just the conversion factor that lets you plug in pounds and inches instead of kilograms and meters. In metric the formula is BMI = weight (kg) ÷ height (m)², and both give the same answer.
Worked example. Say you're 5 ft 10 in and weigh 160 lb. First convert your height to inches: 5 × 12 + 10 = 70 in. Then:
BMI = 703 × 160 ÷ (70 × 70) = 112,480 ÷ 4,900 = 22.96 → rounded to 23.0.
That falls in the Normal band, so no surprises there.
The CDC weight categories for adults are fixed: Underweight below 18.5, Normal from 18.5 up to 24.9, Overweight from 25.0 to 29.9, and Obesity at 30.0 and above. This tool also gives you the healthy weight range for your exact height — for 5 ft 10 in that's about 129 to 174 lb — so you can see your target span, not just a single label.
The most common mistake people make is leaving height in feet instead of converting to total inches. If you square 5.10 (treating five-foot-ten as a decimal) you get a wildly wrong BMI. Always turn your height into inches first: feet × 12 + inches. This calculator does that step for you, so just enter the feet and inches separately.
A few honest caveats: BMI doesn't tell muscle from fat, so very muscular athletes can read "overweight" while carrying little fat, and it can under-flag older adults who've lost muscle. It's a screening number, not the whole story — pair it with your waist measurement, how you feel, and a conversation with your doctor.
📖 See also: Body Fat Percentage: How to Measure It at Home
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Imperial: BMI = 703 × weight (lb) ÷ height (in)² • Metric: BMI = weight (kg) ÷ height (m)² • Height in inches = feet × 12 + inches • Healthy weight (lb) = BMI × height (in)² ÷ 703 • CDC bands: <18.5 Underweight · 18.5–24.9 Normal · 25.0–29.9 Overweight · ≥30 Obesity
📰 Formula
• Imperial: BMI = 703 × weight (lb) ÷ height (in)² • Metric: BMI = weight (kg) ÷ height (m)² • Height in inches = feet × 12 + inches • Healthy weight (lb) = BMI × height (in)² ÷ 703 • CDC bands: <18.5 Underweight · 18.5–24.9 Normal · 25.0–29.9 Overweight · ≥30 Obesity
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Entering height as a decimal (5.10) instead of converting to total inches (70).
- Forgetting the 703 factor when using pounds and inches.
- Squaring height in feet rather than inches.
- Treating BMI as a body-fat measurement — it's a screening ratio, not a diagnosis.
💡 Tips
- Convert height to inches first: feet × 12 + inches, then square that number.
- Use the healthy weight range, not just the category, to set a realistic target.
- Re-check the same time of day on the same scale to track trends fairly.
Embed this calculator on your site
Copy the code below and paste it into the HTML of your site or blog.
<iframe src="https://www.calcnimbus.com/embed/bmi-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How do I calculate BMI in pounds and inches?
BMI = 703 × weight in pounds ÷ (height in inches)². For 160 lb at 70 in: 703 × 160 ÷ 4,900 = 23.0.
What is a healthy BMI range?
For adults the CDC counts 18.5 to 24.9 as the normal (healthy) range. Below 18.5 is underweight and 25 or higher is overweight.
What BMI is considered overweight?
A BMI of 25.0 to 29.9 is classified as overweight. A BMI of 30.0 or above is classified as obesity under CDC guidelines.
What is a good BMI for my height?
BMI uses the same 18.5–24.9 healthy band at every height. The pound range changes: 5 ft 4 in is about 108–145 lb, while 6 ft 0 in is about 136–184 lb.
Is BMI accurate for everyone?
No. BMI doesn't separate muscle from fat, so athletes can read high and older adults can read low. It's a screening tool, not a body-fat measurement or diagnosis.
How do I convert my height to inches for BMI?
Multiply feet by 12 and add the leftover inches. 5 ft 10 in = 5 × 12 + 10 = 70 inches. Use that figure, not the decimal 5.10.
What does the 703 in the BMI formula mean?
703 is the conversion factor that lets the metric formula work with pounds and inches. It makes 703 × lb ÷ in² match kg ÷ m².
Can BMI tell me how much body fat I have?
No. BMI only compares weight to height. For body fat percentage you need a different method like calipers, a DEXA scan, or bioimpedance.
How often should I check my BMI?
Once a month is plenty for tracking trends. Day-to-day weight swings from water and food make daily BMI checks noisy and unhelpful.