How to Convert Celsius to Fahrenheit

Direct answer

Converting Celsius into Fahrenheit

To convert Celsius to Fahrenheit, multiply the Celsius temperature by 9/5 and then add 32. For example, 20°C multiplied by 9/5 equals 36, and 36 plus 32 equals 68°F.

Celsius and Fahrenheit use different degree sizes and different zero points. The conversion therefore requires both multiplication and addition.

The same method works for positive temperatures, negative values, whole numbers, decimals, weather readings, oven settings, body temperatures, and scientific measurements.

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Standard calculation

Celsius-to-Fahrenheit conversion formula

Standard formula °F = (°C × 9/5) + 32

Equivalent decimal form: °F = (°C × 1.8) + 32.

Multiplication by 9/5 adjusts the size of the temperature interval. One Celsius degree of change equals 1.8 Fahrenheit degrees of change.

Adding 32 adjusts for the different zero points. Zero degrees Celsius equals 32 degrees Fahrenheit rather than zero degrees Fahrenheit.

Correct order

Multiply the Celsius value first. Add 32 only after the multiplication has been completed.

Manual method

How to convert Celsius to Fahrenheit step by step

Use 25°C as an example.

01

Write the Celsius temperature

Begin with 25°C and preserve any negative sign or decimal places.
02

Multiply by 9

Calculate 25 × 9 to get 225.
03

Divide by 5

Divide 225 by 5 to get 45.
04

Add 32

Add 32 to 45. The final result is 77°F.

Multiplying directly by 1.8 produces the same result: 25 × 1.8 + 32 = 77°F.

Worked calculations

Examples of converting Celsius to Fahrenheit

Convert 0°C to Fahrenheit

Calculation (0 × 9/5) + 32 = 32°F

Zero degrees Celsius equals exactly 32 degrees Fahrenheit.

Convert 10°C to Fahrenheit

Calculation (10 × 9/5) + 32 = 50°F

Ten degrees Celsius equals exactly 50 degrees Fahrenheit.

Convert 20°C to Fahrenheit

Calculation (20 × 9/5) + 32 = 68°F

Twenty degrees Celsius equals exactly 68 degrees Fahrenheit.

Convert 30°C to Fahrenheit

Calculation (30 × 9/5) + 32 = 86°F

Thirty degrees Celsius equals exactly 86 degrees Fahrenheit.

Convert 100°C to Fahrenheit

Calculation (100 × 9/5) + 32 = 212°F

One hundred degrees Celsius equals exactly 212 degrees Fahrenheit.

Below-zero temperatures

How to convert negative Celsius values

Keep the negative sign during the multiplication step and add 32 afterward.

Convert −10°C

Negative-temperature example (−10 × 9/5) + 32 = 14°F

Negative 10 degrees Celsius equals 14 degrees Fahrenheit.

Convert −20°C

Negative-temperature example (−20 × 9/5) + 32 = −4°F

Negative 20 degrees Celsius equals negative 4 degrees Fahrenheit.

Convert −40°C

Equal-scale point (−40 × 9/5) + 32 = −40°F

Celsius and Fahrenheit have the same numerical value at negative 40 degrees.

Decimal temperatures

How to convert decimal Celsius temperatures

Use the complete decimal Celsius value in the formula and round only the final Fahrenheit result.

Convert 22.5°C

Decimal example (22.5 × 1.8) + 32 = 72.5°F

Twenty-two and one-half degrees Celsius equals 72.5 degrees Fahrenheit.

Convert 36.7°C

Decimal example (36.7 × 1.8) + 32 = 98.06°F

Thirty-six point seven degrees Celsius equals 98.06 degrees Fahrenheit.

Decimal precision is particularly useful for body temperature, laboratory data, thermostats, and technical readings.

Mental conversion

How to estimate Celsius in Fahrenheit mentally

A simple estimate doubles the Celsius value and adds 30. This method is quick but not exact.

10°C About 50°F

10 × 2 + 30

20°C About 70°F

Exact result is 68°F

30°C About 90°F

Exact result is 86°F

A closer estimate multiplies Celsius by 1.8 and adds 32. To approximate multiplication by 1.8 mentally, double the Celsius value and subtract 10% of the doubled result.

Example with 25°C

Double 25 to get 50. Subtract 5 to get 45, then add 32 to get the exact result of 77°F.

Accuracy check

Common Celsius-to-Fahrenheit mistakes

Adding 32 before multiplying

The correct order is multiplication first, followed by addition.

Using multiplication alone

Multiplying by 1.8 adjusts degree size but does not account for the different zero points.

Dropping a negative sign

Preserve the sign throughout the calculation.

Using 9/5 as 9 divided by the full expression

Multiply the Celsius value by 9, divide that result by 5, and then add 32.

Rounding the Celsius value first

Keep the original temperature until the Fahrenheit calculation has been completed.

Related Celsius-to-Fahrenheit guides

Questions and answers

Frequently asked questions

How do I convert Celsius to Fahrenheit?

Multiply Celsius by 9/5 and then add 32.

What is 20 degrees Celsius in Fahrenheit?

Twenty degrees Celsius equals 68 degrees Fahrenheit.

What is negative 10 Celsius in Fahrenheit?