BMI Calculator

Category: Vital Signs & Health Indicators
- April 12, 2025
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Calculate your Body Mass Index and check your weight category

cm
kg
Your BMI
0.0
Weight category will appear here
Underweight Normal Overweight Obese
16 18.5 25 30 40

What Your BMI Means

Enter your height and weight to calculate your BMI and see your weight category.

Additional Health Metrics

Healthy Weight Range
0 - 0 kg
Based on BMI 18.5-24.9
Body Surface Area
0 m²
Estimated using Mosteller formula

What is Body Mass Index (BMI)?

Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m² where kg is a person's weight in kilograms and m² is their height in meters squared.

How BMI is Calculated

Metric Formula:

BMI = Weight(kg) á Height²(m²)

Example: For a person who is 175 cm tall and weighs 75 kg:
BMI = 75 ÷ (1.75 × 1.75) = 24.5

Imperial Formula:

BMI = [Weight(lb) ÷ Height²(in²)] × 703

Example: For a person who is 5'9" (69 inches) tall and weighs 165 pounds:
BMI = (165 ÷ (69 × 69)) × 703 = 24.4

Purpose of BMI

BMI is a screening tool that can indicate whether a person might be at an unhealthy weight for their height. It's widely used by health professionals to identify potential weight problems in adults and children.

BMI is particularly useful for tracking weight status across populations and identifying individuals who may be at increased risk for health problems due to their weight.

BMI Categories

BMI values are used to categorize individuals as underweight, normal weight, overweight, or obese. For adults 20 years and older, BMI is interpreted using standard categories that are the same for all ages and both men and women.

BMI Range Weight Category Health Risk
Below 16.0 Severe Underweight Severe health risk
16.0 - 18.4 Underweight Increased risk
18.5 - 24.9 Normal Weight Lowest risk
25.0 - 29.9 Overweight Increased risk
30.0 - 34.9 Obese Class I High risk
35.0 - 39.9 Obese Class II Very high risk
40.0 and above Obese Class III Extremely high risk

Children and Teens

For children and teens (aged 2-19), BMI is interpreted differently. Age and gender-specific percentiles are used because children's body composition varies as they age and differs between boys and girls.

Note:

This calculator provides BMI categories for adults. For children and teens, consult with a healthcare provider for proper BMI percentile interpretation.

Limitations of BMI

While BMI is a useful screening tool, it has several limitations and should not be the only measure used to determine if someone is at a healthy weight.

BMI Doesn't Consider:

  • Body Composition: BMI doesn't distinguish between muscle and fat. Athletes with high muscle mass may have a high BMI but low body fat.
  • Fat Distribution: Where fat is located on the body matters. Abdominal fat (visceral fat) poses greater health risks than fat in other areas.
  • Age: BMI may overestimate body fat in older adults who have lost muscle mass.
  • Ethnicity: Some ethnic groups may have different body compositions and health risks at the same BMI value.
  • Pregnancy: BMI is not valid during pregnancy.

Additional Measurements

For a more complete assessment of health risks related to weight, other measurements can be helpful:

  • Waist circumference
  • Waist-to-hip ratio
  • Body fat percentage
  • Blood pressure, cholesterol, and blood sugar levels

Important:

BMI is just one screening tool and should be used alongside other assessments. Always consult with healthcare professionals for personalized health advice.

Crunch the Numbers, Check Your Health: Using a BMI Calculator

The BMI Calculator is a quick and simple tool that helps you figure out your Body Mass Index. That might sound fancy, but it’s just a way of checking if your weight is in a healthy range for your height. You pop in your weight and height, click a button, and boom—you get a number. That number tells you which group you fall into: underweight, normal, overweight, or obese.

Why does this matter? Because knowing your BMI can help you make better choices for your health. It’s not about looks or judgment. It’s about information. Maybe you’re wondering if you’re on the right track, or maybe your doctor mentioned it. This tool can give you a clear picture in just a few seconds—without needing a math textbook.

Let’s be real: things like the Mosteller formula, or the metric vs. imperial systems, don’t exactly sound exciting. But when they’re working behind the scenes to calculate your BMI and give you other stats like Body Surface Area, they become pretty helpful—especially when you want numbers that actually mean something to you.

Your BMI Toolbox: What It Can Do

Here’s what this calculator is packing:

  • ✅ BMI Calculation – Based on your height and weight (either in cm/kg or in/lb).
  • ✅ Weight Category – Tells you if your BMI falls into underweight, normal, overweight, or different levels of obesity.
  • ✅ Healthy Weight Range – Shows the weight range you should aim for based on your height.
  • ✅ Body Surface Area (BSA) – A bonus stat that’s used in medical settings, calculated using the Mosteller formula.
  • ✅ Unit Switching – Choose between metric and imperial systems, depending on what you’re used to.
  • ✅ Reset Option – Start over easily whenever you need to.

Real-Life Wins (And No, You Don’t Need a Calculator for That)

This isn’t just for gym lovers or people deep into fitness routines. It’s helpful in everyday life:

  • 📚 For School Projects: Studying health in science class? A BMI calculator gives you fast answers without needing a long explanation or digging through books.
  • 🛒 Shopping Smarter: If you're working on your health goals, knowing your BMI might help you decide what kind of food or workout gear to look for.
  • 🧮 Quick Checks at Home: Wondering if that recent weight change is a big deal? Punch in your numbers and see where you stand.
  • 🩺 Helpful for Doctor Visits: Bring your BMI info with you to appointments. It might even impress your doc.

Example: Let’s say you’re 160 cm tall and weigh 60 kg. Enter your numbers, hit "Calculate BMI," and the calculator tells you your BMI is 23.4—right in the "Normal Weight" zone. No guesswork.

Tap, Type, Done! (How to Use It)

Here’s the step-by-step guide to using the BMI Calculator like a pro:

  1. Pick your unit system: metric (cm/kg) or imperial (in/lb).
  2. Select your gender and enter your age.
  3. Type in your height and weight in the spaces provided.
  4. Hit the “Calculate BMI” button.
  5. Check your results—your BMI score, category, healthy weight range, and Body Surface Area will all appear.
  6. Want to try again? Hit “Reset” and enter new numbers.

Easy. Fast. No headaches.

The Final Equation

At the end of the day, this BMI Calculator isn’t trying to be a bombastic know-it-all or act like the beacon of health advice. It’s just a friendly tool that gives you useful info in seconds. Think of it like a quick math friend who skips the boring parts and gives you straight answers—without burying you in numbers or charts.

Whether you’re tracking your progress, helping out with a school project, or just curious, the BMI Calculator keeps things clear and simple. And that’s a big win—especially in a world that loves to overcomplicate things.