Direct answer
What is the Celsius-to-Fahrenheit formula?
The Celsius-to-Fahrenheit formula is °F = (°C × 9/5) + 32. You can also write it as °F = (°C × 1.8) + 32.
The formula has two parts because Celsius and Fahrenheit use different degree intervals and different zero points.
Multiplication by 9/5 changes the interval size. Adding 32 shifts the result to the Fahrenheit scale.
Enter a positive, negative, whole, or decimal Celsius temperature.
Main equation
The standard Celsius-to-Fahrenheit equation
Multiply by 9, divide by 5, and add 32.
The values 9/5 and 1.8 are equivalent.
For 30°C, substitute 30 for the Celsius variable:
Thirty degrees Celsius equals 86 degrees Fahrenheit.
Degree intervals
Why does the formula multiply by 9/5?
The interval between the freezing and boiling points of water is divided into 100 Celsius degrees but 180 Fahrenheit degrees under standard conditions.
From 0°C to 100°C
From 32°F to 212°F
Equivalent to 1.8
A temperature change of 1°C therefore equals a temperature change of 1.8°F. A change of 10°C equals a change of 18°F.
A change of 10°C equals a change of 18°F, but a reading of 10°C equals 50°F because the scale offset must also be included.
Scale offset
Why does the formula add 32?
Celsius and Fahrenheit assign different values to the same freezing point. Water freezes at 0°C but 32°F under standard conditions.
After the degree interval has been adjusted by multiplying by 9/5, adding 32 shifts the value to the Fahrenheit starting point.
The formula correctly maps 0°C to 32°F.
Without adding 32, the formula would incorrectly make 0°C equal 0°F.
Formula applications
Worked examples using the formula
Convert 5°C
Convert 15°C
Convert 25°C
Convert 37°C
Convert 200°C
Below-zero calculations
How the formula handles negative Celsius values
Negative values use the same equation. The negative sign remains attached to the Celsius number during multiplication.
Negative 15 degrees Celsius equals 5 degrees Fahrenheit.
At −40, the multiplication and offset produce the same numerical value:
Therefore, −40°C equals −40°F.
Opposite direction
What is the Fahrenheit-to-Celsius formula?
Reverse the offset first and then reverse the interval conversion.
Subtract 32 before multiplying by 5/9.
For 68°F:
Sixty-eight degrees Fahrenheit equals 20 degrees Celsius.
Temperature differences
Converting a temperature change
When converting only a temperature difference rather than an actual scale reading, do not add 32. The offset affects scale readings but not the size of a temperature change.
| Celsius change | Fahrenheit change |
|---|---|
| 1°C | 1.8°F |
| 2°C | 3.6°F |
| 5°C | 9°F |
| 10°C | 18°F |
| 20°C | 36°F |
An oven temperature increase from 180°C to 190°C is a change of 10°C, equivalent to a change of 18°F.
Continue reading
Related Celsius-to-Fahrenheit guides
Questions and answers
Frequently asked questions
What is the Celsius-to-Fahrenheit formula?
The formula is °F = (°C × 9/5) + 32.
Why do you add 32?
Adding 32 adjusts for the different zero points of the Celsius and Fahrenheit scales.
Why do you multiply by 9/5?
The Fahrenheit degree interval is 1.8 times the Celsius degree interval.
Do you add 32 when converting a temperature difference?
No. Multiply a Celsius temperature change by 9/5 without adding 32.
Convert a temperature
Use the Celsius to Fahrenheit Converter
Enter any positive, negative, whole, or decimal Celsius temperature to calculate Fahrenheit instantly.
Open Celsius to Fahrenheit ConverterLast updated: July 27, 2026