Temperature Converter

°F = (25 × 9/5) + 32 = 77 °F
K = 25 + 273.15 = 298.15 K

What does this temperature converter do?

Type a temperature in any scale and every other scale updates at the same instant. This free converter from ÆON Toolhub covers the three everyone uses, Celsius, Fahrenheit, and Kelvin, plus five historical and engineering scales: Rankine, Réaumur, Newton, Rømer, and Delisle. It also writes out the calculation step by step with your own numbers, and a colour thermometer rises and shifts from blue to red as the temperature climbs.

Everything runs in your browser, updates live, and accepts a comma or a dot as the decimal separator, so it works the same whether the page is in English or translated.

How do you convert Celsius to Fahrenheit?

Multiply by 9/5 (that is 1.8) and add 32. Written as a formula, °F = (°C × 9/5) + 32. So 100°C is 100 × 1.8 + 32 = 212°F, the boiling point of water.

To reverse it, subtract 32 first, then multiply by 5/9: °C = (°F - 32) × 5/9. The one temperature that reads the same on both scales is -40°, where the two lines cross.

For a rough estimate in your head, double the Celsius value and add 30. At 20°C that gives 70 against a true 68°F, which is close enough for weather but not for cooking, because the real multiplier is 1.8 rather than 2.

How do you use it?

Type in any box. Enter a value in Celsius, Fahrenheit, or any other scale. That box becomes the source and the rest fill in automatically.

Use a preset. Tap Freezing, Room, Body, Boiling, or Oven for common temperatures.

Check the step by step. Below the fields, the conversion is written out with your numbers so you can see exactly how the result was reached.

Read the thermometer. The coloured bar shows roughly where the temperature sits, cool blues low down, warm reds up high.

Celsius to Fahrenheit conversion chart

Every 5 degrees from -40°C to 100°C, with Kelvin alongside:

A few reference points worth remembering: water freezes at 0°C (32°F), a comfortable room sits near 20°C (68°F), normal body temperature is about 37°C (98.6°F), and water boils at 100°C (212°F).

What are the oven temperature conversions?

Recipes are where this conversion bites most often. Note that oven dials use rounded numbers, so the exact conversion and the dial marking differ slightly. Both are shown here:

The classic case is 180°C, which converts exactly to 356°F but appears on dials as 350°F, gas mark 4. Using the dial number is fine: ovens are not precise to a few degrees anyway.

What about Kelvin and the other scales?

Kelvin starts at absolute zero, the coldest possible temperature, so K = °C + 273.15. It has no negative values and is the standard scale in science. Rankine is the Fahrenheit-based equivalent used in some US engineering, where absolute zero is 0°R and water freezes at 491.67°R.

Réaumur, Newton, Rømer, and Delisle are older scales you will mostly meet in history or old texts. Delisle even runs backwards, with 0°De at boiling point and larger numbers as it gets colder. Including them makes this a complete temperature converter rather than just a C-to-F tool.

Why is -40 the same on both scales?

Because the two scales cross there. Fahrenheit rises 1.8 degrees for every 1 Celsius degree but starts 32 higher, and those two effects cancel out at exactly -40. It is the quickest way to sanity-check any converter: type -40 in either box and the other must show -40 too.

Your data stays private

The converter is fully client-side. It uses the exact conversion formulas and keeps full precision while calculating, rounding only the numbers you see. Nothing you type is uploaded, logged, or stored, and it clears when you close the tab. It also keeps working offline once the page has loaded.