BMI Calculator

Calculate your Body Mass Index using the WHO formula. Enter height and weight to...

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cm
kg
Your BMI
24.2
Normal

Your BMI is 24.2, which is in the Normal weight range.

BMI is a general screening tool, not a diagnosis.

1518.525303540+
Healthy Range
53.5 - 72 kg
Category
Normal

WHO BMI Categories (Adults 18+)

Underweight
< 18.5
Normal
18.5-24.9
Overweight
25-29.9
Obese I
30-34.9
Obese II
35-39.9
Obese III
40+
BMI Formula & Calculation
Metric Formula
BMI = weight (kg) / height (m)^2
Imperial Formula
BMI = 703 x weight (lb) / height (in)^2
Your Calculation
70 / (1.70)^2 = 24.2215, rounds to 24.2

Recommendation

You're at a healthy weight. Maintain your lifestyle with balanced nutrition.

Disclaimer: BMI is a screening tool, not a diagnostic measure. It doesn't account for muscle mass, bone density, age, or gender. For children and teens, use BMI-for-age percentiles. Always consult a healthcare provider for personalized health advice.

Quick answer

BMI (Body Mass Index) is a number from your weight and height that screens whether you are underweight, normal, overweight, or obese. This calculator runs fully in your browser and updates the instant you type. Metric BMI divides weight in kilograms by height in meters squared, and imperial BMI multiplies weight in pounds by 703 then divides by height in inches squared. For example, 70 kg at 1.75 m gives a BMI of 22.9, which lands in the normal range of 18.5 to 24.9.

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Calculator Features

Instant Calculation - Results appear as you type - no submit button
100% Private - All calculations in your browser, no data sent anywhere
Show Your Work - Expandable formula section shows exact calculation
Mobile Friendly - Compact UI fits on phone screens without scrolling
Color Gradient Scale - Visual indicator shows your position on the BMI spectrum
Smart Warnings - Detects child-sized measurements and shows appropriate notice

Why Use BMI Calculator?

WHO Standard Formula

Uses the official World Health Organization BMI formula, weight in kg divided by height in meters squared, with the standard category thresholds.

Visual BMI Spectrum

Color-coded gradient scale shows exactly where your BMI falls from underweight (blue) through normal (green) to obese (red).

Metric & Imperial Units

Switch between kg/cm and lb/ft-in with one click. Both use the same underlying WHO formula for consistent results.

Shows Your Calculation

See the exact math: your weight, height, raw BMI value, and rounded result. Full transparency in how your BMI is computed.

Child Height Warning

Automatically detects heights below 140cm and warns that standard adult BMI categories don't apply to children.

Healthy Weight Range

Calculates your ideal weight range based on your height and BMI 18.5-24.9 (normal category).

When to Use BMI

Health Screening

Quick initial assessment before doctor visits. Know your BMI category beforehand.

Weight Goal Setting

Calculate your target weight for normal BMI range based on your height.

Progress Tracking

Track BMI changes over weeks/months as part of fitness or weight management.

Form Completion

Many health forms, insurance applications, and fitness programs ask for BMI.

How It Works

1

Choose Metric or Imperial

Select your preferred unit system. Metric uses centimeters and kilograms; Imperial uses feet-inches and pounds.

2

Enter Height & Weight

Type your measurements. Results calculate instantly as you type - no button to click.

3

Read Your BMI

See your BMI score (to 1 decimal place), category name, position on the color scale, and healthy weight range.

4

Review the Calculation

Expand the formula section to see exactly how your BMI was calculated with raw and rounded values.

Important Notes

BMI Has Limits

BMI can't measure body composition. Athletes, elderly, and pregnant women may get misleading results. It's a screening tool, not a diagnosis.

Consistent Measuring

For tracking: weigh yourself same time daily (morning, after bathroom, before food). Use same scale. Weekly averages are more meaningful than daily fluctuations.

Focus on Trends

A single BMI reading is less important than the trend over time. Moving from 28 to 26 over 6 months shows real progress regardless of exact category.

Frequently Asked Questions

Divide your weight in kilograms by your height in meters squared. In imperial units, multiply your weight in pounds by 703 and divide by your height in inches squared. Example: 70 kg divided by (1.75 m x 1.75 m) = 22.9.
A BMI from 18.5 to 24.9 is the normal, healthy range for most adults. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese.
BMI is an accurate quick screen of weight relative to height, but it cannot tell muscle from fat. A muscular athlete can read overweight despite low body fat, so treat BMI as a starting point, not a diagnosis. For a full picture, use body composition tests such as DEXA or calipers.
Underweight is a BMI below 18.5, Normal is 18.5 to 24.9, Overweight is 25 to 29.9, and Obese is 30 or above. Obesity is split into Class I (30 to 34.9), Class II (35 to 39.9), and Class III (40 and above).
The formula is identical for both. Women typically carry a higher body fat percentage than men at the same BMI, but the WHO categories apply to both sexes equally.
No. This tool uses adult WHO categories. Children and teens need BMI-for-age percentiles that account for growth, so consult a pediatrician. When the height entered looks child-sized, the calculator shows a reminder.
For a normal BMI of 18.5 to 24.9, a healthy weight is 18.5 to 24.9 times your height in meters squared. At 170 cm that is roughly 53 to 72 kg, and at 180 cm it is roughly 60 to 81 kg. The calculator shows your exact range as you type.

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