BMI Calculator

Simple, fast and easy

Result

Result: Fill in the fields

Classification: Fill in the fields

Ideal weight: Fill in the fields

BMI Calculator – Online, Fast and Free

Want to discover your Body Mass Index (BMI) quickly and reliably? Fastools offers a free online BMI calculator that provides instant results, detailed interpretation, and health tips, directly in your browser, with no registration or downloads required.

Simply enter your weight and height, click 'Calculate', and get the result instantly with clear explanations of your BMI classification.

Our BMI tool helps students, health professionals, and anyone interested in monitoring body weight, providing reliable and easy-to-understand information.

How to use the BMI calculator?

1️⃣ Enter your weight in kilograms.
2️⃣ Enter your height in meters.
3️⃣ Click 'Calculate' to see the result instantly.
4️⃣ Check your BMI interpretation and health tips.

Why use the Fastools calculator?

✅ Completely free and online
✅ Fast and accurate results
✅ Detailed interpretation to understand your BMI
✅ Ideal for students, health professionals, and curious minds
✅ Works directly in your browser, no downloads or registration needed

Benefits of using our BMI calculator

📊 Evaluate your weight in relation to your height simply and reliably
⚡ Save time with instant calculations
🎯 Avoid common mistakes in manual calculations
💻 Access from any device: computer, tablet, or smartphone

Can I use the calculator to monitor my health?

Yes! The tool is perfect for anyone who wants to monitor weight, maintain healthy habits, and track their Body Mass Index regularly.

Start calculating your BMI online, free, and reliably now with Fastools!

How BMI is calculated

Expression:

$$\text{IMC} = \frac{\text{peso }}{\text{altura}^2}$$

Where:

Variable Unit of measurement Symbol

BMI Kilograms per square meter Kg/m²

weight Kilograms Kg

height Meter m

Variable	Unit of measurement	Symbol
BMI	Kilograms per square meter	Kg/m²
weight	Kilograms	Kg
height	Meter	m

BMI Classification Table for adults

#	Classification	BMI (kg/m²)	Description
1	Underweight	Less than 18.5	Insufficient body weight for height. Increased risk of health problems.
2	Normal weight	18.5 to 24.9	Adequate weight for height. Low risk of weight-related health problems.
3	Overweight	25,0 a 29,9	Excess weight for height. Moderate increased risk of chronic diseases.
4	Obesity Grade I	30,0 a 34,9	Mild obesity. High risk of diseases such as diabetes, hypertension, and cardiovascular diseases.
5	Obesity Grade II	35,0 a 39,9	Moderate obesity. Very high risk of chronic diseases and complications.
6	Obesity Grade III	Greater than or equal to 40.0	Severe or morbid obesity. Extremely high risk of serious diseases and reduced life expectancy.

Note that, if the BMI value is, for example 24.95, it will be considered 'Normal weight', since overweight starts from a BMI of 25.00.

Fun facts about BMI

BMI was created in 1832 by Adolphe Quetelet, a Belgian astronomer and mathematician.
Originally, it was not intended for individual diagnosis, but for population studies.
The World Health Organization (WHO) adopted BMI as a global standard in 1995.

Used in medical check-ups, scientific research, and even life insurance.
Assists in the early detection of health risks such as diabetes and heart diseases.
Fundamental for epidemiological analysis and public health planning.

Does not differentiate muscle mass from body fat.
May underestimate risks in people with abdominal fat.
Less effective for children, the elderly, and high-performance athletes.

Small changes in height strongly impact BMI.
Alternatives like WHR (waist-hip ratio) assess fat distribution.
Exams like bioimpedance and DEXA provide more accurate body analysis.

Studies show that BMI outside the ideal range is associated with lower longevity.
A person can have a normal BMI but be metabolically unhealthy — the famous “skinny fat”.
BMI is just one of the factors used for general health assessment.