BMI Calculator
Calculate your Body Mass Index (BMI) instantly. Enter your height and weight to see your BMI category and healthy weight range. For adults 18 years and older.
This tool is part of our broader calculator collection. You may also find our child BMI calculator and health calculators hub useful.
Your Measurements
Your Results
Assumptions & Limitations
📊 BMI Category Comparison
📋 Calculation Breakdown
| Item | Value |
|---|---|
| Enter your measurements to see the breakdown. | |
Because body weight is a primary factor in daily fluid requirements, you can use your current weight in our Water Intake Calculator to find your baseline hydration target.
How to Use This BMI Calculator
Using this BMI calculator is simple:
- Select your preferred unit system — Choose between Metric (kg/cm) or Imperial (lb/ft/in).
- Enter your weight — Input your current body weight.
- Enter your height — For metric, use centimeters. For imperial, enter feet and inches separately.
- View your results — Your BMI, category, healthy weight range, and any recommended adjustments appear instantly.
The calculator automatically updates as you type, so you can easily adjust values and see how changes affect your BMI.
If you’re calculating BMI for someone under 20, use our child & teen BMI calculator, which interprets results by age and sex.
What is BMI?
Body Mass Index (BMI) is a simple numerical value calculated from your weight and height. It provides a quick screening method to categorize individuals into weight categories that may indicate health risks.
The formula is straightforward:
BMI = Weight (kg) ÷ Height² (m²)
For example, a person weighing 70 kg with a height of 1.75 m would have a BMI of:
70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9
Understanding BMI Categories
The World Health Organization (WHO) defines the following BMI categories for adults:
- Underweight (BMI < 18.5): May indicate nutritional deficiency or underlying health issues. Consider consulting a healthcare provider.
- Healthy weight (BMI 18.5–24.9): Generally associated with lower risk of weight-related health problems.
- Overweight (BMI 25.0–29.9): May increase risk for certain health conditions. Lifestyle modifications may be beneficial.
- Obesity (BMI ≥ 30.0): Associated with higher risk for various health conditions including heart disease, diabetes, and joint problems.
Limitations of BMI
While BMI is a useful screening tool, it has important limitations:
- Doesn’t measure body composition: BMI cannot distinguish between muscle mass, bone density, and fat. Athletes with high muscle mass may have elevated BMI despite low body fat.
- Age considerations: Older adults may have more body fat than younger adults with the same BMI.
- Ethnic variations: Health risks associated with BMI may vary by ethnicity. Research suggests that South Asian populations may face elevated health risks at lower BMI values (around 23+).
- Not suitable for everyone: Pregnant individuals, children, teens, and people with certain medical conditions require different assessment methods.
BMI should be considered alongside other health indicators such as waist circumference, blood pressure, cholesterol levels, and overall lifestyle factors.
Healthy Weight Range
This calculator shows your healthy weight range based on the BMI range of 18.5 to 24.9. This range represents the weight boundaries that would keep your BMI within the “healthy” category for your current height.
If your current weight falls outside this range, the calculator shows how much weight you may need to gain or lose to reach the healthy BMI zone. Remember that these are general guidelines — your ideal weight depends on many individual factors.
Frequently Asked Questions
General guidance about BMI. Consult a healthcare professional for personalized advice.
Q1: Is BMI accurate for athletes?
A: BMI may overestimate body fat in athletes and individuals with high muscle mass. Since muscle weighs more than fat, muscular people may have a high BMI despite having low body fat. For athletes, body composition measurements like body fat percentage may be more meaningful.
Q2: Does BMI apply to all age groups?
A: This calculator is designed for adults aged 18 and older. For children and teenagers, BMI is interpreted differently using age- and sex-specific percentile charts. A child with the same BMI as an adult would fall into a different category based on their age group.
Q3: Why might BMI be less accurate for certain ethnicities?
A: Research indicates that health risks associated with BMI can vary by ethnicity. For example, South Asian populations may experience increased health risks at lower BMI values (starting around 23) compared to the standard WHO cutoffs. Some health organizations recommend different thresholds for specific populations.
Q4: What should I do if my BMI is outside the healthy range?
A: If your BMI indicates underweight, overweight, or obesity, consider consulting a healthcare provider. They can assess your overall health, discuss contributing factors, and recommend appropriate steps. Small, sustainable lifestyle changes in diet and physical activity can make a meaningful difference over time.
Q5: Can BMI predict health problems?
A: BMI is a screening tool, not a diagnostic tool. While higher BMI is statistically associated with increased risk for conditions like heart disease, type 2 diabetes, and certain cancers, it doesn’t directly measure health. Other factors such as fitness level, diet quality, genetics, and metabolic health are also important.
Q6: How often should I check my BMI?
A: For most adults, checking BMI a few times per year is sufficient unless you’re actively working on weight management. Focus on sustainable habits rather than frequent weighing, as weight naturally fluctuates day to day.
Sources & Further Reading
This calculator uses standard BMI formulas and WHO adult BMI categories.