BMI Calculator — Imperial & Metric
Calculate your Body Mass Index in imperial (pounds and feet/inches) or metric (kg, cm) units. Switch units at any time — your values convert automatically — and see your category and healthy weight range instantly.
No uploads • No tracking • No registration
Not a diagnosis: BMI is a simple screening measure based on height and weight only. It doesn't account for muscle mass, body composition or overall health, and it isn't valid for children or teens, whose healthy BMI depends on age and sex-specific growth references. It's not a substitute for professional medical advice.
How It Works
Choose your units
Switch between metric and imperial at any time.
Enter height and weight
Results update automatically as you type.
See your BMI and category
Along with the healthy weight range for your height.
Privacy note: everything happens locally in your browser. Your height and weight are never sent to a server.
The formula
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obesity |
Imperial BMI calculator (pounds and inches)
In the United States, height and weight are usually recorded in feet, inches and pounds rather than centimetres and kilograms. The imperial BMI formula folds in a conversion factor of 703 so you can work directly in those units:
Worked examples
Imperial
154 lb, 5 ft 9 in (69 in)
703 × 154 ÷ (69²) = 108,262 ÷ 4,761
BMI ≈ 22.7 → Normal weight
Metric
70 kg, 175 cm (1.75 m)
70 ÷ (1.75²) = 70 ÷ 3.0625
BMI ≈ 22.9 → Normal weight
The two formulas agree for the same body size — 154 lb ≈ 70 kg and 69 in ≈ 175 cm, so both land around a BMI of 23. The healthy-weight range shown by the calculator is simply the formula solved backwards for a BMI of 18.5 and 24.9 at your entered height.
Frequently Asked Questions
How is BMI calculated?+
In metric units, BMI is weight in kilograms divided by height in metres squared. In imperial units, BMI is 703 × weight in pounds, divided by height in inches squared. Both formulas give the same result for the same body size.
How do I calculate BMI in imperial units (pounds and inches)?+
Convert your height to total inches (feet × 12 + inches), square it, then compute BMI = 703 × weight in pounds ÷ (height in inches)². For example, 154 lb at 5 ft 9 in (69 in): 703 × 154 ÷ (69 × 69) = 108,262 ÷ 4,761 ≈ 22.7, which is in the normal range. This calculator does the conversion and arithmetic for you when you pick the Imperial unit.
What are the standard adult BMI categories?+
Under 18.5 is classified as underweight, 18.5 to 24.9 as normal weight, 25 to 29.9 as overweight, and 30 or above as obesity. These ranges come from widely used adult BMI classifications.
Does BMI diagnose a health condition?+
No. BMI is a simple screening measure based on height and weight only. It does not account for muscle mass, bone density, body composition or overall health, and it cannot diagnose any medical condition. Speak with a healthcare provider for a personalized assessment.
Is BMI accurate for athletes or very muscular people?+
Not reliably. Because BMI only uses height and weight, a muscular person can be classified as overweight or obese even with low body fat, since muscle weighs more than fat for the same volume.
Can I use this calculator for a child or teenager?+
This calculator uses standard adult BMI categories, which are not appropriate for children or teens. BMI interpretation for young people depends on age and sex-specific growth reference charts, which this tool does not provide.
What is a healthy weight range for my height?+
This calculator shows the weight range that corresponds to a BMI between 18.5 and 24.9 for the height you entered, as a reference point rather than a personalized target.
Does this tool save my height or weight?+
No. All calculations happen locally in your browser. Nothing you enter is uploaded, stored or shared.