BMI Calculator – Calculate Your BMI & Ideal Weight Range

Get your BMI and ideal weight range. Works with metric (kg, cm) or imperial (lbs, ft/in). All calculations run locally in your browser.

BMI calculator form

kg
Optional: Age & gender (for contextual messages only)

Privacy-first

All calculations run in your browser. No data is sent to servers. Works offline after first load.

What is BMI?

Body Mass Index (BMI) is a simple formula that estimates body fat based on height and weight. It divides your weight in kilograms by the square of your height in meters. BMI provides a general indication of whether your weight is in a healthy range for your height and is commonly used as a screening tool.

This free BMI calculator runs entirely in your browser. It supports metric and imperial units, converts values when you switch units, and shows your ideal weight range and contextual tips. No data is sent to servers—everything stays on your device. It also works offline after the first load.

BMI categories

Underweight (<18.5)

May indicate underweight. Consider discussing nutrition with a healthcare provider.

Normal (18.5–24.9)

Generally considered a healthy weight range. Maintain balanced nutrition and activity.

Overweight (25–29.9)

May indicate excess weight. Healthcare providers can suggest healthy management strategies.

Obese (30+)

May be associated with health risks. Personalized guidance from a professional is recommended.

Why use this BMI calculator?

Instant results

Calculations update as you type, no button needed.

Privacy-first

100% frontend-only. No data sent to servers.

Offline capable

Works without internet after first load.

Richer insights

Ideal range, percentile context, and lifestyle tips.

BMI limitations

BMI is a useful screening tool but has known limitations. It does not distinguish between muscle and fat, so athletes or people with high muscle mass may have a higher BMI despite being healthy. It also does not account for age, sex, bone density, or fat distribution. BMI is not a diagnostic tool. For comprehensive health assessments, consult a healthcare professional.

Related calculators

Explore these related free tools to enhance your productivity and workflow.

Calorie Calculator

Find your BMR, TDEE, and daily calorie goal with the Mifflin-St Jeor formula. For weight loss, maintenance, or gain.

Percentage Calculator

Calculate percentages, percentage increases, decreases, and find the percentage of a number

Simple Calculator

Perform basic arithmetic operations like addition, subtraction, multiplication, and division instantly

Frequently Asked Questions

How does this BMI calculator work?

Enter your height and weight in either metric (cm/kg) or imperial (ft+in/lbs). The calculator uses the standard formula—weight divided by height squared—and updates results instantly as you type. You get your BMI number, category, ideal weight range, and contextual interpretation. All processing happens in your browser; nothing is sent to any server.

What do BMI categories mean?

BMI categories are: Underweight (below 18.5), Normal (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). These ranges are widely used as a general screening tool. They do not account for muscle mass, bone density, or body composition, so results should be interpreted as approximate guidance rather than a definitive health assessment.

Is my data private when I use this calculator?

Yes. This BMI calculator is fully frontend-only. All calculations run locally in your browser. No measurements, age, or gender data are sent to any server. Optional "Track my BMI locally" stores your inputs only on your device using localStorage. The calculator works offline after the initial page load.

Can I switch between metric and imperial without losing my data?

Yes. When you switch units, the calculator automatically converts your current values. Your height and weight are preserved and shown in the new unit system. No need to re-enter measurements.

What is the ideal weight range?

The ideal weight range corresponds to a BMI between 18.5 and 24.9 for your height. It is a general guideline based on population health research. Individual factors like muscle mass, age, and body composition can affect what is healthy for you. A healthcare provider can offer personalized guidance.

Why does BMI have limitations?

BMI does not distinguish between muscle and fat, nor does it consider bone density or fat distribution. Athletes with high muscle mass may have a higher BMI despite being healthy. BMI is a screening tool, not a diagnostic measure. For a complete health picture, consult a healthcare professional.

Does this calculator work offline?

After the first load, the calculator runs entirely in your browser. No server connection is needed for calculations. You can use it offline, including on mobile devices, as long as the page has been loaded at least once.