BMI Calculator

Calculate your Body Mass Index based on weight and height with metric and imperial support.

The BMI Calculator computes your Body Mass Index using the standard formula: weight in kilograms divided by the square of height in meters. It supports both metric and imperial units, displays your BMI category with a visual color-coded bar, and provides instant results — all processed locally in your browser for complete privacy.

Weight (kg)

Height (cm)

Your data stays in your browser

Tutorial

How to Use the BMI Calculator

Choose Units

Select metric (kg/cm) or imperial (lbs/ft+in) depending on your preference.

Enter Measurements

Type your weight and height into the input fields provided on the form.

Get Results

Click Calculate to see your BMI value and corresponding health category instantly.

Guide

Complete Guide to Body Mass Index

What Is BMI and How Is It Calculated?

Body Mass Index is calculated by dividing your weight in kilograms by the square of your height in meters (BMI = kg/m²). Developed by Adolphe Quetelet in the 1830s, it remains one of the most widely used population-level health screening metrics. A BMI of 22 means your weight is 22 times the square of your height in meters, placing you squarely in the normal range.

BMI Categories and What They Mean

The World Health Organization defines four main BMI categories: Underweight (below 18.5) may indicate nutritional deficiency or underlying illness. Normal weight (18.5–24.9) is associated with the lowest health risks. Overweight (25–29.9) signals increased risk for cardiovascular disease. Obese (30+) carries significantly elevated risk for diabetes, heart disease, and joint problems.

Limitations of BMI

While BMI is a convenient screening tool, it has notable limitations. It does not distinguish between muscle and fat mass, so muscular athletes may be classified as overweight despite low body fat. It also does not account for age, sex, ethnicity, or fat distribution — factors that significantly affect health risk. Use BMI alongside waist circumference and other metrics.

When to Consult a Doctor

If your BMI falls outside the normal range, consult a healthcare provider for a comprehensive assessment. They can evaluate body composition, blood pressure, cholesterol, blood sugar, and other factors that BMI alone cannot capture. A BMI in the overweight or obese range warrants a conversation about lifestyle changes, dietary adjustments, and possible medical interventions.

Sources

Examples

Worked Examples

Example: Normal Weight Calculation

Given: Weight = 70 kg, Height = 175 cm.

Step 1: Convert height to meters: 175 cm = 1.75 m.

Step 2: Square the height: 1.75² = 3.0625.

Step 3: Divide weight by squared height: 70 / 3.0625 = 22.86.

Step 4: Classify: 22.86 falls in Normal (18.5–24.9).

Result: BMI = 22.9 — Normal weight category.

Example: Imperial Units Calculation

Given: Weight = 200 lbs, Height = 5 ft 10 in.

Step 1: Convert weight: 200 × 0.4536 = 90.72 kg.

Step 2: Convert height: (5×12 + 10) × 0.0254 = 1.778 m.

Step 3: Calculate BMI: 90.72 / 1.778² = 28.7.

Step 4: Classify: 28.7 falls in Overweight (25–29.9).

Result: BMI = 28.7 — Overweight category.

Use Cases

Typical Use Cases

Personal Health Checkup

“Use the BMI calculator as part of your regular health monitoring routine. Enter your current weight and height to get a quick snapshot of where you fall on the BMI scale. Track changes over time by checking monthly after weigh-ins to stay aware of trends.”

Fitness Goal Setting

“Before starting a new diet or exercise program, calculate your current BMI to establish a baseline. This helps you set realistic weight goals and measure progress. Knowing your starting category motivates you to work toward the normal range systematically.”

Medical Screening Preparation

“Calculate your BMI before doctor visits to have an informed discussion about your weight status. Healthcare providers use BMI as a first screening tool, so knowing your number in advance helps you prepare questions and understand recommendations better.”

Frequently Asked Questions

?What is a healthy BMI range?

A healthy BMI falls between 18.5 and 24.9. This range is associated with the lowest risk of weight-related health issues for most adults.

?How accurate is BMI as a health indicator?

BMI is a useful screening tool but does not measure body fat directly. Athletes with high muscle mass may have elevated BMI despite being healthy.

?Does BMI apply to children and teenagers?

Children use age- and sex-specific BMI percentiles rather than the adult categories. This calculator is designed for adults aged 18 and over.

?Can I use BMI to track weight loss progress?

Yes, checking your BMI regularly provides a simple way to monitor weight changes over time alongside other measurements like waist circumference.

?What formula does this calculator use?

It uses the standard BMI formula: weight in kilograms divided by height in meters squared. Imperial inputs are converted to metric before calculation.

?Is this BMI calculator free to use?

Yes, this tool is completely free with no registration required, no ads, and no usage limits. Use it as often as you need.

?Is my health data private?

Absolutely. All calculations happen in your browser. No weight, height, or BMI data is sent to any server or stored anywhere.

?Why does BMI not distinguish between muscle and fat?

BMI uses only weight and height, so it cannot differentiate tissue types. For body composition analysis, consider DEXA scans or skinfold measurements.

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