Best Free Online Developer Tools to Use in 2026
A practical, opinionated list of the best free online developer tools worth using in 2026, organized by category so you can find what you need fast.
Aug 08, 2026
BMI Calculator
Calculate Body Mass Index with WHO classification chart and ideal weight range.
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- BMI Calculator
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WHO BMI Classification
| Category | BMI Range | Risk |
|---|---|---|
| Underweight | < 18.5 | Low (but increased risk of other problems) |
| Normal | 18.5 – 24.9 | Average |
| Overweight | 25 – 29.9 | Increased |
| Obese Class I | 30 – 34.9 | High |
| Obese Class II | 35 – 39.9 | Very High |
| Obese Class III | ≥ 40 | Extremely High |
What is BMI?
Body Mass Index (BMI) is a simple measurement calculated from a person's height and weight. It is used as a screening tool to identify possible weight problems in adults.
This tool features:
- Multiple units — Metric (cm/kg) and imperial (ft/in, lbs) units.
- WHO classification — Categorizes BMI into underweight, normal, overweight, and obese classes.
- Visual indicator — Color-coded progress bar showing where your BMI falls.
- Healthy range — Shows ideal weight range for your height.
How to Use
- Enter your height — Choose cm or feet/inches and enter your height.
- Enter your weight — Choose kg or lbs and enter your weight.
- View your BMI — Your BMI value, category, and ideal weight range appear instantly.
Frequently Asked Questions
How is BMI calculated?
BMI is calculated by dividing weight in kilograms by height in meters squared (kg/m²). For imperial units, the formula is (weight in lbs × 703) / (height in inches)².
Is BMI accurate for everyone?
BMI is a general screening tool and may not be accurate for athletes with high muscle mass, pregnant women, the elderly, or children. Consult a healthcare professional for a complete assessment.
What is a healthy BMI?
According to WHO, a BMI between 18.5 and 24.9 is considered normal/healthy weight. Below 18.5 is underweight, and 25 or above is overweight.
Is this tool free to use?
Yes. All processing happens entirely in your browser. No data is sent to any server.
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