Celsius to Fahrenheit Converter
This free temperature converter turns Celsius into Fahrenheit (F = C times 9/5 plus 32) and Fahrenheit into Celsius, and places your value on a dual scale with freezing, body and boiling landmarks.
Fahrenheit
356°F
Where your value sits on both scales
-40°C
-40°F
0°C
32°F
37°C
98.6°F
100°C
212°F
| Landmark | °C | °F |
|---|---|---|
| Scales meet | -40 | -40 |
| Water freezes | 0 | 32 |
| Body temperature | 37 | 98.6 |
| Water boils | 100 | 212 |
Examples
How to use
- 1
Type a temperature in Celsius (or switch the direction to start from Fahrenheit).
- 2
Read the converted value instantly: the tool applies F = C x 9/5 + 32 exactly.
- 3
Spot your value on the dual scale, between the freezing, body and boiling landmarks.
- 4
Use the landmarks table to memorize key pairs, then copy or download the result.
What is the Celsius to Fahrenheit formula?
Two operations, always in this order:
F = C x 9/5 + 32
Multiply the Celsius reading by 9/5, which is 1.8, then add 32. So 20°C gives 20 x 1.8 = 36, plus 32 lands at 68°F. To reverse it, undo the steps backwards: subtract 32 first, then divide by 1.8. So 98.6°F minus 32 is 66.6, divided by 1.8 gives exactly 37°C.
Why 32 and 9/5?
The two scales picked different anchor points. Celsius pins 0 and 100 to water freezing and boiling. Fahrenheit, older by a couple of decades, pinned 32 and 212 to the same two events. Between them sit 100 Celsius degrees but 180 Fahrenheit degrees, and 180 / 100 = 9/5. That is the whole story: an offset of 32 and a step ratio of 1.8.
Which temperatures are worth memorizing?
| Event | °C | °F |
|---|---|---|
| Scales meet | -40 | -40 |
| Water freezes | 0 | 32 |
| Room temperature | 20 | 68 |
| Body temperature | 37 | 98.6 |
| Hot summer day | 35 | 95 |
| Water boils | 100 | 212 |
| Moderate oven | 180 | 356 |
The -40 line is the odd one, the only temperature where both scales read the same number. Plug it in: -40 x 1.8 = -72, plus 32 comes back to -40.
How do you convert C to F in your head?
Double the Celsius, take off 10 percent, add 32. For 20°C: double is 40, minus 4 is 36, plus 32 gives 68°F, exact here. Across weather ranges the shortcut stays within a degree. Reverse it by subtracting 32, halving, then adding 10 percent, so 86°F gives 54, halved to 27, plus 2.7, rounding to 30°C.
How do oven temperatures convert?
Recipes cross the Atlantic constantly, and the oven is where a slip hurts. 180°C, the standard moderate oven in European recipes, is 356°F, which US cooks round to 350°F. A fan oven usually runs about 20°C hotter than its dial says, so a 180°C fan setting behaves like 200°C conventional, or 392°F.
How cold can it actually get?
Temperature has a hard floor: absolute zero, at -273.15°C or -459.67°F. Nothing goes below it, so the converter rejects any value under that mark rather than printing a number with no physical meaning.
How do you read weather in the other unit?
A rough map for travelers: 0°C (32°F) means frost, 10°C (50°F) calls for a jacket, 20°C (68°F) is pleasant, 30°C (86°F) is beach weather, 40°C (104°F) is a heat warning. The Fahrenheit numbers land close to a 0-to-100 comfort scale, which is exactly what its fans like about it. Celsius answers with cleaner science anchors at 0 and 100. Keep whichever intuition you grew up with and let the tool translate the rest.
Parameters
Every field of this tool can be prefilled from the URL. Use these query parameters:
| Parameter | Type | Default |
|---|---|---|
| value | number | 20 |
| direction | cToF | fToC | cToF |
Example : https://www.veltotools.com/conversion/celsius-to-fahrenheit-converter?value=20
API
The same tool is available as a free JSON API, with the same parameters as above. No key, no sign-up.
Frequently asked questions
Updated Jul 17, 2026