Use this professional tool to calculate BMI from height and weight instantly. Understand your health status with our precise Body Mass Index calculator, interactive charts, and comprehensive guide.
Metric (kg, cm)
Imperial (lbs, ft/in)
Select your preferred unit system.
Enter height in centimeters.
Please enter a valid height (50-300 cm).
Enter weight in kilograms.
Please enter a valid weight (20-500 kg).
Enter height in feet and inches.
Please enter a valid height.
Enter weight in pounds.
Please enter a valid weight (40-1000 lbs).
Your Estimated BMI
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Enter Details
Ideal Weight Range
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Diff. from Normal
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Ponderal Index
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*BMI Formula: Weight / Height²
BMI Category Distribution
Underweight
Normal
Overweight
Obese
Standard BMI Categories
Category
BMI Range (kg/m²)
Health Risk
Underweight
< 18.5
Malnutrition Risk
Normal Weight
18.5 – 24.9
Low Risk
Overweight
25 – 29.9
Moderate Risk
Obesity
≥ 30
High Risk
Standard WHO classifications for adults over 20 years of age.
When you calculate BMI from height and weight, you are determining a numerical value that screens for weight categories that may lead to health problems. Body Mass Index (BMI) is a widely used metric established by the World Health Organization (WHO) and utilized by insurance companies, doctors, and health professionals globally to quickly assess if a person has a healthy body weight for a given height.
While not a direct measure of body fat, BMI correlates moderately with more direct measures of body fat. It serves as an inexpensive and easy-to-perform method for screening for weight categories such as underweight, healthy weight, overweight, and obesity. Knowing how to calculate BMI from height and weight is often the first step in formulating a proactive health management plan.
Who should use it? This metric is primarily designed for adult men and women over the age of 20. It is a useful general indicator for the majority of the population, though it has limitations for specific groups such as professional athletes or the elderly.
Calculate BMI from Height and Weight: The Formula
To calculate BMI from height and weight manually, you rely on a simple mathematical relationship between mass and stature. Depending on which measurement system you prefer, the formula changes slightly to maintain accuracy.
Metric Formula
In the metric system, the formula is:
BMI = Weight (kg) / [Height (m)]²
Since most people measure height in centimeters, you typically divide height in centimeters by 100 to get meters before squaring.
Imperial Formula
In the imperial system (common in the United States), the formula is:
BMI = 703 × Weight (lbs) / [Height (in)]²
Variables Table
Variable
Meaning
Unit (Metric)
Unit (Imperial)
Typical Range
W
Body Weight
Kilograms (kg)
Pounds (lbs)
40-150 kg
H
Stature/Height
Meters (m)
Inches (in)
1.4-2.0 m
BMI
Body Mass Index
kg/m²
kg/m²
15-40+
Detailed breakdown of variables used to calculate BMI from height and weight.
Practical Examples: Calculating BMI
To better understand how to calculate BMI from height and weight, let's look at two realistic scenarios.
Example 1: The Metric Calculation
Profile: Sarah is 165 cm tall and weighs 68 kg. Step 1: Convert height to meters: 165 cm / 100 = 1.65 m. Step 2: Square the height: 1.65 × 1.65 = 2.7225. Step 3: Divide weight by squared height: 68 / 2.7225 = 24.97. Result: Sarah has a BMI of roughly 25.0, placing her just on the border between Normal and Overweight.
Example 2: The Imperial Calculation
Profile: Michael is 5 feet 10 inches tall and weighs 185 lbs. Step 1: Convert height to inches: (5 × 12) + 10 = 70 inches. Step 2: Square the height: 70 × 70 = 4,900. Step 3: Divide weight by squared height: 185 / 4,900 = 0.0377. Step 4: Multiply by conversion factor 703: 0.0377 × 703 = 26.5. Result: Michael has a BMI of 26.5, which falls into the Overweight category.
How to Use This Calculator
Our tool simplifies the math so you don't have to manually calculate BMI from height and weight. Follow these steps:
Select Unit System: Choose between Metric (kg/cm) or Imperial (lbs/ft).
Enter Weight: Input your current weight. Ensure it is accurate (measure in the morning for best consistency).
Enter Height: Input your standing height without shoes.
Review Results: The calculator updates instantly. Look at the colored status indicator to see if you fall into the Underweight, Normal, Overweight, or Obese range.
Analyze Data: Check the "Ideal Weight Range" to see what weight would place you in the center of the "Normal" category (BMI 21.7).
Key Factors That Affect BMI Results
While it is useful to calculate BMI from height and weight, the number is a general indicator and does not tell the whole story. Several financial and biological factors influence how this number should be interpreted.
Muscle Mass vs. Fat: Muscle is denser than fat. Athletes often calculate BMI from height and weight and find they are "obese" despite having very low body fat. This is a known limitation.
Age Distribution: As people age, they tend to lose muscle and gain fat. An elderly person might have a "normal" BMI but actually have excess body fat (sarcopenic obesity).
Bone Density: Individuals with larger skeletal frames or higher bone density will naturally weigh more, potentially skewing the BMI calculation upward.
Gender Differences: Women typically have more body fat than men at the same BMI level. However, the standard formula to calculate BMI from height and weight uses the same thresholds for both genders.
Ethnic Variations: Different ethnic groups have different health risks at the same BMI. For example, Asian populations often have higher health risks at a lower BMI compared to Caucasian populations.
Pregnancy: One should never calculate BMI from height and weight using standard charts during pregnancy, as weight gain is necessary and expected.
Frequently Asked Questions (FAQ)
1. Is BMI the best way to measure health?
No, it is a screening tool, not a diagnostic tool. While it is helpful to calculate BMI from height and weight for general population tracking, it does not measure visceral fat or metabolic health directly.
2. Can I use this for children?
No. Children and teens need BMI-for-age percentiles, which compare them to other children of the same age and gender. This calculator is for adults 20+.
3. What is the "Ideal Weight" shown in the results?
The ideal weight range displayed is calculated based on a target BMI range of 18.5 to 24.9, which WHO defines as healthy.
4. Why does the calculator use 703 for Imperial?
The factor 703 converts pounds and inches into the metric kg/m² standard. Without it, the calculation would result in a meaningless number.
5. Does BMI impact life insurance rates?
Yes. Insurance actuaries use BMI as a primary risk factor. A high BMI can lead to higher premiums because it correlates with higher risks of diabetes and heart disease.
6. How often should I calculate BMI from height and weight?
Checking once a month is sufficient. Weight fluctuates daily due to water retention, so daily checking can be misleading.
7. What is the Ponderal Index?
The Ponderal Index is similar to BMI but cubes the height (h³) instead of squaring it. It is sometimes considered more valid for very tall or very short individuals.
8. If I am "Overweight," should I panic?
Not necessarily. If you are muscular or active, you may be healthy. Consult a doctor to measure body fat percentage and waist circumference for a better picture.
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