Conversión de temperatura

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: °F to °C Deduct 32, then multiply by 5, then divide by 9 °C to °F Multiply by 9, then divide by 5, then add 32 (Explanation Below ...)

Typical Temperatures

°C	°F	Description
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)

Explanation

There are two main temperature scales:

°F, the Fahrenheit Scale (used in the US), and
°C, the Celsius Scale (part of the Metric System, used in most other countries)

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

• Boiling water (at normal pressure) measures 100° in Celsius, but 212° in Fahrenheit
• And as water freezes it measures 0° in Celsius, but 32° in Fahrenheit

Like this:

Looking at the diagram, notice:

• The scales start at a different number (0 vs 32), so we will need to add or subtract 32
• The scales rise at a different rate (100 vs 180), so we will also need to multiply

And this is how it works out:

To convert from Celsius to Fahrenheit, first multiply by 180/100, then add 32

To convert from Fahrenheit to Celsius, first subtract 32, then multiply by 100/180

Note: 180/100 can be simplified to 9/5, and likewise 100/180=5/9, so this is the easiest way:

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

We can write that as a formula like this:

Celsius to Fahrenheit	(°C × 9/5) + 32 = °F
Fahrenheit to Celsius	(°F - 32) x 5/9 = °C

Example: Convert 26° Celsius (a nice warm day) to Fahrenheit

First: 26° × 9/5 = 234/5 = 46.8
Then: 46.8 + 32 = 78.8° F

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

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

 

Other Methods That Work

Use 1.8 instead of 9/5

9/5 is equal to 1.8, so you could 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 you 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

• 20x2 = 40
• less 10% is 40-4 = 36
• 36+32 = 68° F

Add 40, Multiply, Subtract 40

Since both scales cross at -40° (-40° C equals -40° F) you can:

• add 40,
• multiply by 5/9 (for °F to °C), or 9/5 (for °C to °F)
• subtract 40

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

• 10+40 = 50
• 50×9/5 = 90
• 90-40 = 50° F

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:

• 0° C → 0+30 → 30° F (low by 2°)
• 10° C → 20+30 → 50° F (exact!)
• 30° C → 60+30 → 90° F (high by 4°)
• 180° C → 360+30 → 390° F (high by 34°, not good)

Examples °F → °C:

• 40° F → 10/2 → 5° C (almost right)
• 80° F → 50/2 → 25° C (low by about 2°)
• 120° F → 90/2 → 45° C (low by about 4°)
• 450° F → 420/2 → 210° C (low by about 22°, not good)