Conversion of Temperature

Quick Celsius (°C) / Fahrenheit (°F) Conversion:

Conversion Tool

Just type a value in either box:

°C:
°F:

 

Or use the Interactive Thermometer,

 

Or this method:

°C to °F Divide by 5, then multiply by 9, then add 32
°F to °C Deduct 32, then multiply by 5, then divide by 9

(Explanation Below ...)

Typical Temperatures

  °C °F Description
  180 356 Moderate Oven
  100 212 Water boils
  40 104 Hot Bath
  37 98.6 Body temperature
  30 86 Beach weather
  21 70 Room temperature
  10 50 Cool Day
  0 32 Freezing point of water
  −18 0 Very Cold Day
  −40 −40 Extremely Cold Day
(and the same number!)
  (bold are exact)  

16 is about 61
28 is about 82

Explanation

There are two main temperature scales:

They both measure the same thing (temperature!), but use different numbers:

Like this:

temperature freeze (0 vs 32) and boil (100 vs 212)

Looking at the diagram, notice:

And so, to convert:

from Celsius to Fahrenheit: first multiply by 180100, then add 32
from Fahrenheit to Celsius: first subtract 32, then multiply by 100180

180100 can be simplified to 95, and 100180 can be simplified to 59, so this is the easiest way:


°C to °F:   Divide by 5, then multiply by 9, then add 32

°F to °C:   Subtract 32, then multiply by 5, then divide by 9


Example: Convert 25° Celsius (a nice warm day) to Fahrenheit

First: 25° / 5 = 5
Then: 5 × 9 = 45
Then: 45 + 32 = 77° F

Example: Convert 98.6° Fahrenheit (normal body temperature) to Celsius

First: 98.6° − 32 = 66.6
Then: 66.6 × 5 = 333
Then: 333 / 9 = 37° C

We can swap the order of divide and multiply if we want, but don't change the add or subtract. So this is also OK:

Example: Convert 98.6° Fahrenheit to Celsius (again)

First: 98.6° − 32 = 66.6
Then: 66.6 / 9 = 7.4
Then: 7.4 × 5 = 37° C

(Same answer as before, was it easier or harder this way?)

We can write each as a formula like this:
Celsius to Fahrenheit:   (°C × 95) + 32 = °F
Fahrenheit to Celsius:   (°F − 32) × 59 = °C
 

Other Methods That Work

Use 1.8 instead of 9/5

9/5 is equal to 1.8, so we can also use this method:

Celsius to Fahrenheit:   °C × 1.8 + 32 = °F
Fahrenheit to Celsius:   (°F − 32) / 1.8 = °C

To make "×1.8" easier we can multiply by 2 and subtract 10%, but it only works for °C to °F:

Celsius to Fahrenheit:   (°C × 2) less 10% + 32 = °F

Example: Convert 20° Celsius (A nice day) to Fahrenheit

 

Add 40, Multiply, Subtract 40

Since both scales cross at −40° (−40° C equals −40° F) we can:

Like this:

Celsius to Fahrenheit:   Add 40, multiply by 9/5, then subtract 40
Fahrenheit to Celsius:   Add 40, multiply by 5/9, then subtract 40

Example: Convert 10° Celsius (A cool day) to Fahrenheit

To remember 9/5 for °C to °F think "F is greater than C, so there are more °F than °C"

 

Quick, but Not Accurate

Celsius to Fahrenheit:   Double, then add 30
Fahrenheit to Celsius:   Subtract 30, then halve

Examples °C → °F:

Examples °F → °C:

 

temperature particles

Footnote: Temperature is a measure of how fast an objects particles are moving.