BMI Calculator

Calculate your Body Mass Index based on WHO standards

Free, accurate, and instant results with personalized health recommendations

Last updated: November 21, 2025
Frank Zhao - Creator
CreatorFrank Zhao
More info
More info
1Metric Units
BMI=weight(kg)height(m)2BMI = \frac{weight(kg)}{height(m)^2}
2Imperial Units
BMI=703×weight(lb)height(in)2BMI = 703 \times \frac{weight(lb)}{height(in)^2}
BMIBody Mass Index
kg / lbWeight Units
m / inHeight Units

What is BMI?

Body Mass Index (BMI) is a simple numerical value derived from your weight and height. It is widely used by healthcare professionals as a screening tool to categorize individuals into weight groups: underweight, normal weight, overweight, and obese.

BMI provides a quick estimate of body fatness and helps identify potential health risks associated with being over or underweight.

Whether you are tracking your fitness journey or just curious about your health status, our BMI calculator provides instant, accurate results based on international standards.

Quick Start Guide

1Step-by-Step Instructions

  • Select Units: Choose between Metric (kg, cm) or Imperial (lb, ft/in).
  • Enter Weight: Type your current weight into the input field.
  • Enter Height: Type your height accurately.
  • Review Result: The calculator updates automatically as you type.

Calculation Example

For a person weighing 70 kg and standing 175 cm tall:

BMIBMI==70/(1.752)70 / (1.75^2)==70/3.062570 / 3.0625==22.8622.86

Result: Normal Weight

Real-World Examples

💪

The Fitness Enthusiast

John is 180 cm tall and weighs 85 kg. He works out regularly.

BMI=85/(1.82)=26.2BMI = 85 / (1.8^2) = 26.2

Status: Overweight (Note: John has high muscle mass)

👩‍💻

The Office Worker

Sarah is 5'4" (162.5 cm) and weighs 130 lbs (59 kg).

BMI=59/(1.6252)=22.3BMI = 59 / (1.625^2) = 22.3

Status: Normal Weight

When to Use

🏥

Health Screening

A quick way to check if your weight is in a healthy range for your height.

📈

Weight Tracking

Monitor changes in your BMI as you progress through a diet or exercise plan.

🩺

Risk Assessment

Identify if you are at higher risk for conditions like heart disease or diabetes.

Tips & Best Practices

✅Do's

  • Measure your height without shoes for accuracy.
  • Weigh yourself at the same time of day (e.g., morning).
  • Use BMI as one of many health indicators, not the only one.

❌Don'ts

  • Don't rely solely on BMI if you are a professional athlete.
  • Don't use this adult calculator for children or teens.
  • Don't panic if your result is slightly outside the normal range.

Calculation Formula

The BMI formula is standardized globally. It measures the relationship between your mass and your height squared.

Metric Formula:

BMI=weight (kg)height2 (m2)BMI = \frac{weight\ (kg)}{height^2\ (m^2)}

Imperial Formula:

BMI=weight (lb)height2 (in2)×703BMI = \frac{weight\ (lb)}{height^2\ (in^2)} \times 703

Variable Definitions:

  • weightweightYour total body mass in kilograms or pounds.
  • heightheightYour vertical stature in meters or inches.
  • 703703A conversion factor used for imperial units to align with metric results.

Related Concepts

BMI Prime

BMI Prime is the ratio of your actual BMI to the upper limit of the "normal" range (usually 25). A BMI Prime of 1.0 means you are at the top of the normal range.

Body Fat Percentage

While BMI estimates fatness, Body Fat Percentage measures it directly. Athletes often have high BMIs but low body fat percentages.

Frequently Asked Questions

Q: Is BMI accurate for muscular people?

A: Not entirely. BMI doesn't distinguish between muscle and fat. Since muscle is denser than fat, very muscular people (like bodybuilders) may have a high BMI even with low body fat.

Q: What is a 'healthy' BMI range?

A: For most adults, a healthy BMI is between 18.5 and 24.9. However, this can vary slightly based on ethnicity and age.

Q: Does BMI apply to children?

A: The basic formula is the same, but the interpretation is different. Children's BMI is compared to percentiles for their age and gender.

Q: Can I use BMI to diagnose health issues?

A: No. BMI is a screening tool, not a diagnostic one. A high BMI may indicate a risk, but a doctor would need to perform further tests (like skinfold thickness or blood pressure) to assess health.

Limitations & Disclaimers

Disclaimer: This BMI calculator is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

  • Does not account for age, gender, or ethnicity.
  • Does not measure body fat percentage or distribution.
  • May overestimate fat in athletes and underestimate it in the elderly.
WHO Obesity Data CDC BMI Information

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BMI Calculator - Calculate Your Body Mass Index Online