Temperature Converter — Free Online Tool
Convert Celsius, Fahrenheit & Kelvin with formulas shown. · No signup · Works on mobile
100% private: your data is processed in your browser. Nothing is uploaded to our servers.
How to use the temperature converter
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Type a temperature into any of the three fields — Celsius, Fahrenheit, or Kelvin.
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The other two fields convert instantly as you type.
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Check the formula line below to see exactly how the conversion works.
What does this tool do?
This free temperature converter switches between Celsius, Fahrenheit, and Kelvin instantly. Type a value in any one scale and the other two update live, with the exact conversion formula displayed — so you get the answer and understand how it was derived.
How does the temperature converter work?
Conversions use exact formulas: °F = °C × 9/5 + 32, and K = °C + 273.15. Fahrenheit and Celsius meet at −40° (the only temperature identical in both scales), while 0 K (−273.15 °C) is absolute zero — the coldest temperature physically possible.
Frequently Asked Questions
What is the formula to convert Celsius to Fahrenheit?
°F = °C × 9/5 + 32. So 20 °C = 20 × 1.8 + 32 = 68 °F. A quick mental estimate: double the Celsius and add 30 (20 °C ≈ 70 °F) — accurate to within a few degrees across the everyday weather range.
What are the key reference temperatures worth memorizing?
Water freezes at 0 °C / 32 °F / 273.15 K and boils at 100 °C / 212 °F at sea level. Body temperature is about 37 °C / 98.6 °F. Room temperature is 20–22 °C / 68–72 °F. And −40° is where Celsius and Fahrenheit are exactly equal.
Is the temperature converter really free?
Yes — 100% free with no hidden charges, trial limits, or premium tiers for core features. You don't need to create an account or enter an email address. The site is supported by non-intrusive display ads, which keeps every tool free for everyone.
Is my data private when using the temperature converter?
Completely. The temperature converter runs entirely in your browser using JavaScript — nothing you type or upload is sent to our servers. When you close the tab, your data is gone. This makes it safe for confidential documents, financial figures, and personal information.
Does the temperature converter work on mobile phones?
Yes. The temperature converter is built mobile-first and works on any phone or tablet with a modern browser — iPhone (Safari), Android (Chrome), and everything in between. The layout adapts to small screens, so buttons and inputs stay easy to tap on a 375px-wide display.
Do I need to install anything to use the temperature converter?
No. The temperature converter works directly in your web browser — no downloads, no extensions, no signup. Just open the page, use the tool, and get your result instantly. It works on Windows, macOS, Linux, ChromeOS, iOS, and Android.