Health & Fitness Calculators
BMI Calculator
Calculate body mass index from height and weight, see the adult category, and understand screening limitations.
US units are selected by default. Switch to metric if needed.
Enter your weight in pounds.
Enter feet only.
Enter the remaining inches.
Calculation assumptions
- *BMI is a screening estimate based on height and weight only.
- *It does not directly measure body fat, muscle mass, or fat distribution.
- *Adult BMI categories may not apply well to children, pregnancy, athletes, older adults, or unusual body composition.
- *BMI does not account for individual health risk, medical history, age-specific needs, or pregnancy status.
- *Use BMI as context, not as a diagnosis or medical recommendation.
Enter your values and press Calculate.
Results and breakdowns will appear here after a valid calculation.
What is BMI?
Body Mass Index (BMI) is a screening estimate based on height and weight. It is often used as a quick population-level reference, but it is not a diagnosis.
Formula: BMI = weight in kilograms / height in meters squared. Example: 70 kg at 1.75 m gives 70 / (1.75 x 1.75) = 22.9.
BMI can be useful for quick adult screening, but it does not directly measure body fat, muscle mass, pregnancy status, age-specific needs, or individual health risk.
How to calculate BMI
Metric formula: BMI = weight kg / height m^2.
US formula: BMI = weight lb x 703 / height in^2.
Example: 180 lb at 5 ft 10 in is 180 x 703 / 70^2 = 25.8.
Adult BMI category chart
These are general adult BMI categories. They are screening ranges, not diagnosis labels.
- Underweight:Below 18.5
- Healthy / normal weight range:18.5 - 24.9
- Overweight range:25.0 - 29.9
- Obesity class 1 range:30.0 - 34.9
- Obesity class 2 range:35.0 - 39.9
- Obesity class 3 range:40.0 or higher
What BMI can and cannot tell you
BMI can show how weight compares with height in a simple way. It can be useful for broad screening and population-level context.
BMI cannot show fat distribution, muscle mass, bone mass, pregnancy status, age-specific needs, or personal health risk. Use it with other context, not alone.
BMI vs body fat percentage
BMI uses only height and weight. Body fat percentage estimates how much of total weight is fat mass. The two numbers can tell different stories, especially for athletes, older adults, or people with high or low muscle mass.
For broader context, compare with the Body Fat Calculator, Ideal Weight Calculator, Calorie Calculator, Macro Calculator, and Heart Rate Zones Calculator.
Limitations of BMI
BMI has important limits. Athletes with high muscle mass may have a high BMI without high body fat, while older adults may have a normal BMI with lower muscle mass. BMI also does not account for pregnancy, children, ethnicity, body frame, or fat distribution.
Users with medical concerns should ask a qualified professional. BMI is one screening estimate, not a diagnosis or personalized health risk assessment.
Common mistakes
- Treating BMI as a diagnosis instead of a screening estimate.
- Using adult BMI categories for children or pregnancy.
- Ignoring body composition, muscle mass, and health context.
- Comparing results without checking that the same units were used.
Quick answers
What this calculator answers
- Result: Calculates BMI and places it in a broad adult BMI category.
- Method: Uses BMI = weight in kilograms divided by height in meters squared.
- Use cases: Useful as a quick adult screening estimate or starting point for a health conversation.
- Limit: BMI is not a diagnosis and does not measure muscle, body fat, pregnancy, age, or individual health status.
- Related guide: Read the BMI guide for what the number can and cannot tell you. what BMI can and cannot tell you
- Body composition: Compare BMI with a body fat estimate for broader context. Body Fat Calculator
Transparency note
Accuracy and limitations
Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.
Health and fitness results are estimates, not medical advice. Formulas simplify real bodies and cycles, so important health decisions should be checked with a qualified clinician.
Reference check
Sources and references
These references provide background context for the topic. They do not replace official advice or documents for personal decisions.
- Adult BMI Calculator
Centers for Disease Control and Prevention
- Assessing your weight and health risk
National Heart, Lung, and Blood Institute
How to Use This Tool
Use these steps to enter the right inputs and interpret the result correctly.
Choose US or Metric units.
Enter your weight and height in the matching unit system.
Press Calculate to see your BMI score and category.
Refer to the adult BMI category chart for broad context.
Use BMI as a screening estimate, not as a diagnosis or full health assessment.
Related Tools
Other helpful tools in the Health & Fitness Calculators category.
Body Fat Calculator
Estimate body fat percentage with Navy circumference or BMI-based methods, reference ranges, and neutral context.
Ideal Weight Calculator
Compare common ideal-weight formulas with a healthy BMI range and clear estimate limitations.
Calorie Calculator
Estimate BMR, TDEE, maintenance calories, and simple deficit or surplus planning targets.
Macro Calculator
Estimate daily protein, carbs, fat, calories, and macro split targets from body stats, goals, and activity.
Heart Rate Zones Calculator
Calculate Zone 2, max-HR, and Karvonen heart-rate-reserve zones for general fitness planning.
Related Guides
Background reading and explanations related to BMI Calculator.
BMI Limits: What BMI Can and Cannot Tell You
Understand BMI as a screening estimate and where body composition context matters.
BMI Explained (What It Means and When It Misleads You)
What your BMI score really means.
Ideal Weight Is an Estimate, Not a Diagnosis
Read ideal-weight formula results as rough context, not medical conclusions.
Frequently Asked Questions
Common questions about BMI Calculator and how to read the result.
Is BMI accurate for everyone?
BMI is a general screening estimate for most adults. It can mislead for children, pregnancy, athletes, older adults, or people with unusual body composition.
What is a healthy BMI?
For many adults, 18.5 to 24.9 is commonly labeled normal weight, but health context matters and BMI alone is not a diagnosis.
Can BMI diagnose a health condition?
No. BMI does not diagnose, treat, or manage medical conditions.
Should I worry if my BMI is high?
A high BMI can be a reason to look at broader health context, but a clinician can interpret it alongside other measurements and history.
Does BMI measure body fat?
No. BMI uses only height and weight, so it does not directly measure body fat or muscle mass.
Which units can I use?
You can use US units with pounds, feet, and inches or metric units with kilograms and centimeters.