About the Celsius to Fahrenheit
This Celsius to Fahrenheit converter turns any temperature in degrees Celsius (°C) into degrees Fahrenheit (°F), and also shows the equivalent in kelvin. Type a value — positive, negative or with decimals — and the answer updates immediately, together with the formula filled in with your number so you can check the working.
It is handy when you are reading a weather forecast from abroad, following a recipe or oven setting written in Celsius, checking a fever reading on a metric thermometer, or doing science homework. The reference table underneath lists the temperatures people look up most, from −40 °C (where both scales meet) to the boiling point of water.
The conversion is exact: the Fahrenheit scale is defined from the Celsius scale, so there is no approximation beyond the decimals shown. For a quick mental estimate you can double the Celsius value and add 30, but that shortcut drifts by several degrees at high and low temperatures.
With the default inputs, the fahrenheit is 77 °F. Change any value above to recalculate instantly.
How to use the celsius to fahrenheit
- 1Enter the temperature in degrees Celsius (negative values are fine).
- 2Read the Fahrenheit result and the kelvin equivalent.
- 3Check the working line to see the formula applied to your number.
- 4Use the reference table for common cooking, weather and body temperatures.
Formula and method
A Fahrenheit degree is 5/9 the size of a Celsius degree, so the Celsius value is first multiplied by 9/5 (or 1.8) to change the size of the degree. Then 32 is added because water freezes at 0 °C but at 32 °F — the two scales start from different zero points.
Kelvin uses Celsius-sized degrees but starts at absolute zero, so K = °C + 273.15. The scales cross at exactly −40, where −40 °C equals −40 °F.
- °C
- Temperature in degrees Celsius
- °F
- Temperature in degrees Fahrenheit
- K
- Temperature in kelvin (°C + 273.15)
Worked examples
Normal body temperature: 37 °C
37 × 9/5 = 66.6, and 66.6 + 32 = 98.6 °F — the traditional figure for normal body temperature. In kelvin that is 37 + 273.15 = 310.15 K.
Where the scales meet: −40 °C
−40 × 9/5 = −72, and −72 + 32 = −40 °F. This is the only temperature where Celsius and Fahrenheit read the same number.
Oven at 180 °C
180 × 1.8 = 324, plus 32 gives 356 °F. Recipes usually round this to 350 °F, which is the standard "moderate oven" setting in the US.
Frequently asked questions
What is the formula to convert Celsius to Fahrenheit?+
Multiply the Celsius temperature by 9/5 (1.8) and then add 32. For example, 20 °C × 1.8 = 36, and 36 + 32 = 68 °F.
Is there an easy way to convert Celsius to Fahrenheit in my head?+
Double the Celsius number and add 30. It is close for everyday weather — 20 °C gives 70 °F versus the exact 68 °F — but the error grows at high temperatures such as oven settings.
What is 0 °C in Fahrenheit?+
0 °C is 32 °F, the freezing point of water at normal atmospheric pressure. 100 °C is 212 °F, the boiling point of water at sea level.
At what temperature are Celsius and Fahrenheit equal?+
The two scales are equal at −40 degrees. Solving C = C × 9/5 + 32 gives C = −40, so −40 °C is exactly −40 °F.
Is 30 °C hot?+
30 °C is 86 °F, which most people consider a hot summer day. 20–22 °C (68–72 °F) is typical room temperature, and 40 °C (104 °F) is extreme heat.