Conversion of Temperature - Celsius to Fahrenheit (2024)

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

Typical Temperatures

(only bold are exactly the same)

Some Tricks:

Daily Temperatures: these three conversions "flip the digits" (accurate within 1°):

°C °F
28 ⇄ 82
16 ⇄ 61
04 ⇄ 40

Oven Temperatures: in the range 150 to 200 °C we can double °C to get °F (accurate within 8°F):

Going the other way: for the range 300 to 400 °F we can halve °F to get °C (accurate within 4°C).

Explanation

There are two main temperature scales:

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

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 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 we get this:

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:

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

Add 40, Multiply, Subtract 40

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

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

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

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)

1041, 1042, 1043, 1044, 3724, 3725, 3726, 3727, 3728, 3729