BMI is a screening tool, not a diagnosis. It doesn’t distinguish muscle from fat, so athletes and very lean or very muscular people can score outside normal. Use alongside waist, activity, and clinician input.

BMI Calculator

Name: Toolspy
Address: US
Telephone: +1-800-TOOLSPY
Price range: Free
Rating: 4.8

A fast online BMI calculator. Enter your height and weight in metric or imperial units and see your Body Mass Index and category — in your browser, no signup.

Use this BMI calculator to compute your Body Mass Index quickly. Supports both metric (kg / cm) and imperial (lb / ft / in). The result shows your BMI value, category, and the healthy weight range for your height.

BMI is a useful screening tool for adults but it’s only one signal. Combine with waist measurement, activity level, and a clinician’s advice for a fuller picture of your health.

BMI calculator — height and weight inputs with BMI result and category

Getting started

How to calculate your BMI

Three quick steps.

1. Pick units

Metric (kg, cm) or Imperial (lb, ft / in).

2. Enter measurements

Height and weight — decimals allowed.

3. Read result

BMI value, category, and your healthy weight range.

Reference

Adult BMI categories (WHO)

A standard reference for adults 20+.

BMI range	Category	Notes
Under 18.5	Underweight	Consider a check-in with a clinician if this is unexpected.
18.5 – 24.9	Normal	Typical healthy range for most adults.
25.0 – 29.9	Overweight	A common range; lifestyle factors matter most.
30.0 – 34.9	Obesity Class I	Talk to a clinician about personalised guidance.
35.0 – 39.9	Obesity Class II	Higher health risk. Professional advice recommended.
40+	Obesity Class III	Seek medical guidance for a plan.

Ranges follow standard WHO categories for adults. Children and teens use different, age-specific percentiles.

The maths

BMI formula

Metric: BMI = weight(kg) / height(m)²

Imperial: BMI = 703 × weight(lb) / height(in)²

The tool handles both — just enter the numbers and pick units.

Heads up

Common pitfalls

BMI doesn’t measure body composition

Muscle is denser than fat. Athletes often score ‘overweight’ or ‘obese’ despite being fit.

Adult vs child interpretations

BMI categories here are for adults. Children and teens use age-specific percentiles — check a paediatric chart.

Snapshot, not a trend

A single BMI value is one data point. Tracking over weeks / months tells you more than one reading.

Not a medical verdict

BMI is a screening tool. Decisions should include waist, activity, bloodwork, and a clinician’s input.

Overview

What this tool supports

Feature checklist

A factual summary of what the BMI calculator does.

Feature	Supported	Notes
Metric units (kg, cm)	Yes	BMI in kg/m².
Imperial units (lb, ft/in)	Yes	Converted to BMI automatically.
Adult BMI categories	Yes	WHO ranges for healthy / overweight / obesity.
Healthy weight range	Yes	Shows the weight range that would land in the healthy BMI.
Instant live result	Yes	Updates as you type.
Account required	No	No signup, no install.

Frequently Asked Questions

Is the BMI calculator free to use?

Does it support both metric and imperial?

What BMI range is healthy?

Is BMI accurate?

What about children and teens?

Does the tool save my height or weight?

Community

User reviews

No reviews yet. If you used the tool, you can share feedback on our feedback page.

Ready to check your BMI?

Enter your height and weight — see your BMI, category, and healthy range.