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
Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur with instant results and formula display.
- Home
- Converter Tools
- Temperature Converter
Conversion Formulas
C to F: °C × 9/5 + 32 = °F
F to C: (°F - 32) × 5/9 = °C
C to K: °C + 273.15 = K
K to C: K - 273.15 = °C
C to Ré: °C × 4/5 = °Ré
Ré to C: °Ré × 5/4 = °C
C to °R: (°C + 273.15) × 9/5 = °R
°R to C: (°R - 491.67) × 5/9 = °C
What is Temperature Conversion?
Temperature conversion allows you to convert between different temperature scales. The most common scales are Celsius (°C), Fahrenheit (°F), and Kelvin (K), but this tool also supports Rankine (°R) and Réaumur (°Ré).
This tool features:
- Five temperature scales — Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur.
- Instant conversion — Results update in real-time as you type.
- Formula display — See the conversion formula used for each calculation.
- Bidirectional — Enter any value and all others update automatically.
How to Use
- Enter a temperature — Type a value in any of the five temperature fields.
- View converted values — All other fields update automatically with the converted values.
- Check the formula — The formula section shows the conversion formula used.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 and add 32. For example, 100°C × 9/5 + 32 = 212°F.
What is the difference between Kelvin and Rankine?
Both are absolute temperature scales. Kelvin uses the same increment as Celsius, while Rankine uses the same increment as Fahrenheit. Absolute zero is 0 K or 0 °R.
What is the Réaumur scale used for?
The Réaumur scale is primarily used in some European food industry applications and in the production of certain dairy products. Water freezes at 0°Ré and boils at 80°Ré.
Is this tool free to use?
Yes. All processing happens entirely in your browser. No data is sent to any server.
Last updated: 17 Aug 2026
Related Tools
Try These Tools Too
Blog
Latest from Our Blog
How to Choose a Hash Algorithm for Data Security
A practical decision guide to choosing the right hash algorithm: MD5, SHA-1, SHA-2, SHA-3, bcrypt, argon2, PBKDF2, and SRI, with comparisons and clear recommendations.
Aug 08, 2026
CSS vs Tailwind CSS: Which One Should You Use?
A thorough, practical comparison of hand-written CSS and Tailwind CSS: learning curve, maintainability, performance, team workflows, and when each approach wins.
Aug 08, 2026
How to Optimize Core Web Vitals for Your Website
Learn practical, step-by-step techniques to improve LCP, INP, and CLS on your website. A developer-focused guide with real measurements and fixes.
Aug 08, 2026
How to Use Base64 Encoding in Real Projects
Learn practical, production-ready ways to use Base64 encoding: data URLs for images, JWT payloads, API tokens, and email attachments, with real code examples.
Aug 08, 2026
AES Encryption Explained: How It Works and Why It Matters
Learn how AES encryption works, the differences between AES-128, AES-192, and AES-256, and how to encrypt and decrypt data online.
Jun 23, 2026