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BMI Calculator

Calculate your Body Mass Index based on height and weight.

Last updated: June 13, 2026

Calculator

Unit System

Weight

lbs

Height (feet)

Height (inches)

Results

Your BMI22.8

Normal weight

How to Use This Calculator

1Select your preferred unit system (Imperial or Metric).
2Enter your weight in pounds (or kilograms if metric).
3Enter your height in feet and inches (or centimeters if metric).
4Your BMI and weight category display instantly — no button required.

Formula Explanation

BMI is calculated by dividing weight by height squared. The imperial formula multiplies by 703 to convert from pounds/inches to the standard BMI scale.

BMI = (weight ÷ height²) × 703 (Imperial) BMI = weight ÷ height² (Metric, kg/m²)

Variables:

weightBody weight in pounds (imperial) or kilograms (metric)

heightHeight in inches (imperial) or meters (metric)

703Conversion factor for imperial units

Worked Examples

Example 1: 150 lbs, 5'8" (Imperial)

1. Weight = 150 lbs
2. Height = 68 inches (5'8")
3. BMI = (150 ÷ 68²) × 703 = (150 ÷ 4624) × 703

Result: BMI = 22.8 (Normal weight)

Example 2: 90 kg, 180 cm (Metric)

1. Weight = 90 kg
2. Height = 1.80 m
3. BMI = 90 ÷ (1.80)² = 90 ÷ 3.24

Result: BMI = 27.8 (Overweight)

Why Use This Calculator

Quick screening tool for weight-related health risks used by healthcare providers worldwide.
Helps track weight changes over time when paired with regular measurements.
Provides an objective starting point for discussions with your doctor about healthy weight goals.
Works for adults 18+ of all genders with a simple, universally recognized scale.

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Tips & Best Practices

BMI does not differentiate between muscle and fat — athletes may have a high BMI but low body fat.
Measure height first thing in the morning when your spine is least compressed for the most accurate reading.
Weigh yourself at the same time of day, ideally in the morning before eating, for consistent results.
Pair BMI with waist circumference for a more complete picture of health risk.

Common Mistakes to Avoid

❌ Using the metric formula with imperial units or vice versa.

✅ Always check your unit system selection before reading results.

❌ Measuring height in shoes or with thick socks, which inflates the reading.

✅ Measure height barefoot against a flat wall for accuracy.

❌ Treating BMI as a definitive health diagnosis rather than a screening tool.

✅ Use BMI as one data point and consult a healthcare provider for full assessment.

Frequently Asked Questions

What is a healthy BMI range?

A healthy BMI is between 18.5 and 24.9 according to the World Health Organization. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is classified as obese. However, BMI is just one indicator of health.

Is BMI accurate for athletes and muscular people?

BMI can overestimate body fat in muscular individuals because it cannot distinguish muscle from fat. A bodybuilder with low body fat may still have a BMI in the overweight range. In these cases, body fat percentage is a better metric.

Does BMI apply to children?

Children and teens use a different BMI system called BMI-for-age percentile, which accounts for normal growth patterns. This calculator is designed for adults aged 18 and older.

How often should I check my BMI?

If you are actively managing your weight, checking monthly is reasonable. Otherwise, tracking BMI at annual physical exams is sufficient for most adults.

Can BMI predict heart disease or diabetes?

A BMI over 25 is associated with increased risk for heart disease, type 2 diabetes, and other conditions. However, BMI alone does not predict disease — other factors like diet, exercise, and genetics play significant roles.

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Embed This Calculator

Add the BMI Calculator to your website for free. Copy the code below and paste it into your HTML.

Width

Height

<iframe src="https://redicalc.com/embed/fitness/bmi-calculator" width="100%" height="600" style="border:none;border-radius:12px;box-shadow:0 1px 3px rgba(0,0,0,0.1);" title="BMI Calculator — RediCalc.com" loading="lazy" allowtransparency="true"></iframe>

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Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.

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