BMI Calculator

What is the Free BMI Calculator?

The free BMI Calculator computes your Body Mass Index from your height and weight — in metric (cm / kg) or imperial (ft, in / lb) units. Enter your Height and Weight, and see your BMI value alongside its WHO category: Underweight, Normal weight, Overweight, Obese Class I, II, or III. A visual scale shows where your BMI sits relative to the healthy range (18.5–24.9).

• → Get a quick health screening reference before a medical appointment
• → Track BMI changes over a weight loss or fitness programme
• → Check whether a child or adult meets insurance or medical eligibility criteria
• → Calculate BMI for health and wellness forms that ask for it
• → Compare BMI before and after dietary or lifestyle changes

How to Use the Free BMI Calculator

1. 1 Select your unit system: Metric (cm and kg) or Imperial (feet, inches, and pounds).
2. 2 Enter your height in the Height field. For metric, enter centimetres. For imperial, enter feet and inches in the two separate fields.
3. 3 Enter your weight in the Weight field (kg for metric, lb for imperial).
4. 4 Read your BMI value (displayed to one decimal place) and the corresponding WHO category — colour-coded from blue (Underweight) through green (Normal) to red (Obese Class III).

Key Features

• ⚖️
  Metric & Imperial

  Switch between cm/kg and ft-in/lb with a single toggle.
• 🏷️
  WHO categories

  Result is labelled: Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese Class I–III (30+).
• 🎨
  Colour-coded result

  The BMI category is colour-coded for instant visual reference.
• ⚡
  Instant calculation

  BMI updates as you type height or weight.
• 🆓
  Free, no signup

  No account required.

Example Usage

Height: 175 cm | Weight: 78 kg

BMI: 25.5
Category: Overweight (25 – 29.9)

Frequently Asked Questions about the Free BMI Calculator

What is the free BMI Calculator?

Calculate your Body Mass Index and understand your weight category.

Is the BMI Calculator free to use?

Yes, the BMI Calculator is completely free. No account, subscription, or signup is required — ever.

Does my data get uploaded anywhere?

No. The BMI Calculator runs entirely in your browser. Your data is never sent to any server.

Does it work offline?

Yes. Once the page has loaded, the tool works without an internet connection.

Which browsers are supported?

All modern browsers — Chrome, Firefox, Safari, and Edge. No plugins or extensions required.

Is BMI an accurate measure of health?

BMI is a simple screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, age, sex, or fat distribution. Athletes with high muscle mass may have a high BMI without excess fat. People with low BMI but high visceral fat may be metabolically unhealthy. Use BMI as a starting point and consult a healthcare professional for a full assessment.

What is a healthy BMI?

The WHO defines a healthy BMI range as 18.5–24.9 for adults. BMI below 18.5 is classified as underweight; 25–29.9 as overweight; 30–34.9 as Obese Class I; 35–39.9 as Obese Class II; and 40 or above as Obese Class III. For children and teenagers, age- and sex-specific percentile charts are used instead.

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