Temperature Converter
Convert temperatures between Celsius, Fahrenheit and Kelvin instantly. Free and in-browser.
Edit any field — the others update live. Examples: 100 °C, 212 °F, 373.15 K.
How to use the Temperature Converter
- 1Click into the Celsius, Fahrenheit, or Kelvin field for the unit you already know.
- 2Type your temperature value, including a minus sign or decimals if needed (for example -40 or 98.6).
- 3Watch the other two fields update instantly as you type, with no submit or refresh required.
- 4Read your converted results directly, or clear the field and enter a new number to convert again.
- 5Copy any result by selecting it, or note the freezing and boiling markers to double-check your figure.
About the Temperature Converter
The Temperature Converter turns any value between Celsius, Fahrenheit, and Kelvin in real time, right inside your browser. You type a number into one field and the other two update the instant the value changes, so there is no submit button to hunt for and no waiting on a network round trip. Every calculation happens locally in JavaScript on your own device. Nothing you type is ever uploaded to a server, logged, or stored, which means you can use it offline once the page has loaded and you never have to worry about where your numbers went.
Under the hood it uses the exact standard formulas rather than rough approximations. Fahrenheit to Celsius is (F minus 32) multiplied by 5/9; Celsius to Fahrenheit is C times 9/5 plus 32; Kelvin is simply Celsius plus 273.15. Because Kelvin is anchored to absolute zero, the tool can warn you when a value drops below that physical floor (-273.15 C or -459.67 F), which no real substance can reach.
The everyday uses are wide. Bakers and home cooks translate a recipe that lists 220 C into the 428 F their oven dial shows. Travelers reading a foreign weather forecast in Celsius can feel what 35 C means in Fahrenheit before packing. Students in chemistry and physics move between Kelvin and Celsius for gas-law problems. Nurses, HVAC technicians, brewers, and 3D-printing hobbyists all cross these scales daily. Anyone comparing a US spec sheet against a metric one benefits too.
A few practical tips: watch the rounding, since the display trims long decimals but the underlying math keeps full precision, so 98.6 F reads as a clean 37 C. Body temperature, freezing (0 C / 32 F), and boiling (100 C / 212 F) are handy anchor points to sanity-check any result. Negative values and decimals are fully supported, so -40 correctly shows the famous point where Celsius and Fahrenheit meet. Because it is client-side, the converter loads fast, costs nothing, needs no account, and keeps working even on a plane or in a lab with no signal.
Frequently asked questions
Which formulas does the converter use to stay accurate?
It uses the exact standard equations: (F-32) x 5/9 for Fahrenheit to Celsius, C x 9/5 + 32 for the reverse, and C + 273.15 for Kelvin. There are no approximations, so results match scientific and textbook values.
Why does 37 Celsius show as exactly 98.6 Fahrenheit but a value like 21 C looks slightly off?
The display rounds long decimals for readability while the internal math keeps full precision. 21 C is truly 69.8 F; some conversions simply produce repeating decimals that get trimmed on screen.
Can I enter negative temperatures or values below absolute zero?
Yes, negatives and decimals are fully supported, so you can convert -40 and see it match on both Celsius and Fahrenheit. If you go below absolute zero (-273.15 C), the tool flags it since no real temperature can exist there.
Does the converter work without an internet connection?
Once the page has loaded, yes. All conversion runs in your browser with JavaScript, so it keeps working offline on a plane, in a lab, or anywhere with no signal.
Is Kelvin handled correctly given it has no negative range in practice?
Kelvin is calculated from Celsius plus 273.15 and is measured from absolute zero, so 0 K equals -273.15 C. The tool converts Kelvin against both other scales and treats it as an absolute scale, not a shifted everyday one.
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Frequently asked questions
Which units?+
Celsius, Fahrenheit and Kelvin — change any one and the others update.