BMI (Body Mass Index) is a measure of body fat based on height and weight. It's calculated as weight divided by height squared. BMI provides a general indicator of whether weight is healthy for height. Standard categories: Underweight (<18.5), Normal (18.5-24.9), Overweight (25-29.9), Obese (≥30).

Is BMI accurate for everyone?

BMI is a general indicator and may not be accurate for everyone. It doesn't account for muscle mass, bone density, or body composition. For athletes, very muscular individuals, or elderly people, BMI may not reflect actual health. BMI is most accurate for average adults with average body composition.

What's the difference between Metric and Imperial?

Metric uses kilograms (kg) for weight and centimeters (cm) for height. Imperial uses pounds (lbs) for weight and inches for height. The BMI formula adjusts for units: Metric: weight(kg) / height(m)², Imperial: (weight(lbs) / height(inches)²) × 703. Both produce the same BMI value.

Can I use BMI for medical diagnosis?

No, BMI is not a diagnostic tool. It's a general health indicator. For medical diagnosis, health assessments, or health advice, consult healthcare professionals. BMI should be used as a screening tool, not a definitive health measure.

What if my BMI is in the overweight or obese category?

BMI categories are general guidelines. If your BMI is in overweight or obese range, consider consulting healthcare professionals for personalized advice. BMI is one indicator—other factors (diet, exercise, medical history) are important. Focus on overall health, not just BMI number.

BMI Calculator - Calculate Body Mass Index Free

When to Use This Tool

Use this when:

You want to calculate your Body Mass Index (BMI) from height and weight
You're tracking health and fitness goals and need BMI measurements
You need to determine your BMI category (underweight, normal, overweight, obese)
You're monitoring weight changes and want to track BMI over time
You're filling out health forms that require BMI information
You want to assess general health status using BMI as an indicator
You're working on fitness goals and need BMI calculations

Don't use this if:

You need medical diagnosis or health advice (consult healthcare professionals)
You require body composition analysis beyond BMI (use specialized body composition tools)
You need BMI calculations for children or adolescents (use age-specific BMI calculators)
You want to calculate BMI for athletes or very muscular individuals (BMI may not be accurate)
You require detailed health assessments or medical evaluations

What is a BMI Calculator?

A BMI (Body Mass Index) calculator computes your BMI value from your height and weight measurements, then categorizes the result according to WHO classifications (underweight, normal, overweight, obese). Our tool processes everything in your browser — no health data is transmitted.

BMI is the most widely used screening tool for categorizing weight status in adults. While BMI has limitations (it doesn't distinguish between muscle and fat mass), it remains a standard health metric used by healthcare providers, insurance companies, fitness professionals, and public health organizations worldwide.

This tool is useful for health-conscious individuals monitoring their weight category, fitness enthusiasts tracking body composition trends over time, healthcare students learning about BMI classifications, nutritionists providing initial assessments to clients, and anyone preparing for a health screening or insurance application.

Compared to healthcare provider calculations (which require an appointment), fitness tracker apps (which often require accounts and collect health data), or online calculators with invasive ads and data collection, PureXio calculates BMI instantly with zero data collection or health information exposure.

The tool supports both metric (kg/cm) and imperial (lbs/feet-inches) measurements, displays the BMI value with WHO category classification, shows a visual BMI scale indicating where your value falls, provides healthy weight range information for your height, and explains BMI limitations. All calculations follow WHO standard BMI formulas.

Best for: calculating BMI from height and weight. Metric and imperial units. WHO category classification with visual scale. Zero health data collected.

How to Calculate BMI

Select unit system: Metric (kilograms and centimeters) or Imperial (pounds and inches)

Enter your height and weight in the selected units. For metric: height in cm, weight in kg. For imperial: height in inches, weight in lbs

Click 'Calculate BMI' to compute your BMI. Review your BMI value and category (underweight, normal, overweight, obese). BMI ranges are displayed for reference

Common Use Cases

Calculate personal BMI: Enter height and weight to see BMI and category

Track fitness progress: Calculate BMI over time to monitor weight changes

Health assessment: Use BMI as a general health indicator

Fill out health forms: Get BMI value for forms requiring BMI information

Fitness goals: Calculate BMI to set or track fitness goals

Weight management: Monitor BMI as part of weight management program

General health awareness: Calculate BMI for general health awareness

Features

Calculate BMI from height and weight using standard BMI formula

Support for Metric units (kilograms, centimeters) and Imperial units (pounds, inches)

Display BMI category: Underweight (<18.5), Normal (18.5-24.9), Overweight (25-29.9), Obese (≥30)

Show BMI ranges for each category for reference

Real-time calculation—BMI updates as you enter values

Color-coded BMI categories for easy interpretation

100% private—all calculations happen in your browser

Limitations & Constraints

BMI is a general indicator—doesn't account for muscle mass, bone density, or body composition

BMI may not be accurate for athletes, very muscular individuals, or elderly people

BMI doesn't consider age, gender, or ethnicity—standard formula applies to all

BMI is not a diagnostic tool—consult healthcare professionals for medical advice

BMI categories are general guidelines—individual health varies

Troubleshooting

BMI calculation shows error or doesn't work

Solution: Check that height and weight are entered as valid numbers. Ensure you selected the correct unit system (Metric or Imperial). Height and weight must be positive numbers. Verify unit selection matches your input values. Prevention: Enter valid numbers and select correct unit system.

BMI seems incorrect or unexpected

Solution: Verify height and weight are entered correctly. Check unit system matches your input (Metric: cm/kg, Imperial: inches/lbs). BMI formula is: Metric: weight(kg) / height(m)², Imperial: (weight(lbs) / height(inches)²) × 703. Ensure values are in correct units. Prevention: Double-check height and weight values and unit system.

BMI category doesn't match expectations

Solution: BMI categories are standard ranges: Underweight (<18.5), Normal (18.5-24.9), Overweight (25-29.9), Obese (≥30). If category seems wrong, verify height and weight are correct. BMI is a general indicator—individual health varies. For athletes or very muscular people, BMI may not be accurate. Prevention: Understand that BMI is a general indicator, not a complete health assessment.

Need BMI for children or adolescents

Solution: This tool uses standard BMI formula for adults. Children and adolescents require age and gender-specific BMI calculations. Use specialized pediatric BMI calculators for accurate BMI calculations for children. Prevention: Use age-specific BMI calculators for children.

BMI doesn't account for muscle mass

Solution: BMI is a general indicator based on height and weight—it doesn't distinguish between muscle and fat. For athletes or very muscular individuals, BMI may show as overweight even with low body fat. Use body composition analysis for more accurate assessments. Prevention: Understand BMI limitations for muscular individuals.