Best Tips to Convert Celsius to Fahrenheit Without Doing Any Math

Laelia Yang April 28, 2022 | 03:02

Just memorize these simple ways to convert the Fahrenheit temperature to the Celsius temperature without a calculator!

As you know, all the important countries in the world use Fahrenheit: We use it, plus the Bahamas, Liberia, Palau, Cayman Islands, Marshall Islands, and the Federated States of Micronesia. Again, all the world’s most prominent countries.

But since lots of other countries still haven’t gotten on the Fahrenheit train, you’re gonna encounter temperatures in Celsius from time to time. And converting Celsius to Fahrenheit takes math: It’s the Celsius temperature times 1.8, plus 32. No thanks.

So here’s a trick to “convert” Celsius to Fahrenheit without using any math. You won’t get the EXACT temperature, but you’ll get a decent ballpark number.

What is Celsius?

Let’s start with the basics: what is celsius? Celsius—sometimes called the centigrade scale—is the most common method of quantifying temperature. It is employed by the International System of Units, or the metric system, which is used in all countries except:

United States
Bahamas
Belize
Cayman Islands
Liberia

Named after Anders Celsius, this system has been around since the early 1700s. In today’s form, you will see it depicted as a degree symbol followed by a capital ‘c’ ( °C).

What is Fahrenheit?

If you live in one of the five countries listed above, you’re probably already familiar with Fahrenheit. The Fahrenheit system’s zero degrees (written as 0°F) came about from the temperature of brine, a combination made from equal parts ice, water, and salt.

Daniel Gabriel Fahrenheit proposed this scale in 1724, and it was later adopted as the primary measurement in the above five countries, as well as on various islands. Unlike Celsius, Fahrenheit is a component of the Imperial system (think of inches, pounds, and gallons). That said, it is not nearly as prevalent in the science community as its metric system counterpart.

Celsius vs Fahrenheit: Key Differences

Before we explain how to convert Celsius to Fahrenheit (and Fahrenheit to Celsius), let’s review the main differences between the two temperature scales.

Celsius (written as °C and also called Centigrade) is the most common temperature scale in the world, used by all but five countries. It’s part of the International System of Units (SI), or what you might know as the metric system, which is typically used in science classes (think centimeters, meters, kilograms, milliliters, etc.) and in science as a whole.

By contrast, Fahrenheit (written as °F) is only used officially by five countries in the world:

United States
Belize
Cayman Islands
Palau
Bahamas

Fahrenheit is not part of the metric system; rather, it’s part of the Imperial system, which includes forms of measurements such as inches, feet, pounds, gallons, etc. Moreover, unlike Celsius, it is not typically used in science.

Why do some recipes use Celsius and others Fahrenheit?

Recipes either appear in Celsius and/or Fahrenheit due to their country of origin's use of the metric system (as Europe does) or imperial units (as the United States does). All countries in the world except for the United States, Myanmar and Liberia use the metric system.

How to Convert Celsius to Fahrenheit (Exact Calculation)

Photo: whas11

If you're looking to get a more precise calculation, you can use this exact formula. You may want to have a calculator handy when you do this.

(Celsius temp. × 1.8) + 32 = Fahrenheit temp.

Begin the conversion by multiplying the temperature in Celsius by 1.8 (or 9/5), then add 32 to your answer to get the Fahrenheit reading.

Here's an example using 30 degrees Celsius.

(30 x 1.8) + 32 = 86 F

How to Convert Fahrenheit to Celsius (Exact Calculation)

When converting Fahrenheit to Celsius, you simply reverse the same equation above. Subtract 32 from the degrees in Fahrenheit, then divide your answer by 1.8.

(Fahrenheit temp. – 32) ÷ 1.8 = Celsius temp.

Here is the formula in action starting with 80 degrees F:

(80 – 32) ÷ 1.8 = 26.6 C (or round up to 27 C)

How to Convert Celsius to Fahrenheit Quickly

This formula will help you make a close estimate for a Fahrenheit temperature when you're converting from Celsius. This is a great formula to do quickly in your head. Simply multiply the Celsius temperature by 2 and add 30 to it:

(Celsius temp. x 2) + 30 = Fahrenheit temp.

Here's an example using 30 degrees C.

(30 x 2) + 30 = 90 degrees F.

This is pretty close to the 86 degrees F reading you'd get using the more precise method (explained later).

How to Convert Fahrenheit to Celsius Quickly

To do a rough approximation of Celsius using Fahrenheit, reverse the earlier formula. Subtract 30 from the Fahrenheit degrees, then divide your answer by 2.

(Fahrenheit temp. – 30) ÷ 2 = Celsius temp.

Let's say the Fahrenheit temperature is 80 degrees. The approximate Celsius temperature would be:

(80 – 30) ÷ 2 = 25 C

Trick to Convert Celsius to Fahrenheit Without Doing Any Math

Photo: YouTube

Here’s the trick:

04 degrees Celsius is 40 degrees Fahrenheit (chilly!)
16 degrees Celsius is 61 degrees Fahrenheit (hoodie weather)
28 degrees Celsius is 82 degrees Fahrenheit (balmy!)
40 degrees Celsius is 104 degrees Fahrenheit (stay inside and crank up the A/C)

For these particular numbers, you’re just reversing the digits: 16 becomes 61, get it? The only weird one is 40, but now that you’ve read it, you get the idea. Four degrees Celsius is 40 Fahrenheit, and 40 Celsius is 104 Fahrenheit.

Now, if you’re on vacation and they tell you it’s going to be 32 today, you know that that’s more than 28 (82 Fahrenheit) but thankfully below 40 Celsius (104 F). It’s tank top and shorts weather.

On the other hand, if it’s going to be 10 degrees, you know that it will be cooler than 61 Fahrenheit (10 is less than 16), but warmer than 40 (10 is more than 4). Bring a jacket, and you’ll be good.

And a fun bonus fact, in case you’re ever vacationing in the Arctic: -40 is -40 in both scales.

What are some ways to convert Celsius to Fahrenheit without a calculator?

Without a calculator, there are many means to convert Celsius to Fahrenheit.

1. By Hand

Multiply the Celsius temperature by 1.8 and add 32 to get the Fahrenheit conversion With this method you get the exact temperature conversion degree.

Example: What is the temperature in Fahrenheit from 10 degrees celsius?

(10*C x 9/5) + 32= *F

(10*C x 1.8) + 32= *F

(18) + 32 = *F

50= F

You find that 10 degrees Celsius is equal to 50 degrees Fahrenheit.

2. Visual Conversion

Use an infographic chart to visually convert Celsius to Fahrenheit. With this method, there are no mathematical calculations necessary.

3. Unconventional Mathematics Formula

Multiply the Celsius degree by 2, subtract by the first digit of the Celsius temperature then add 32. It's an unconventional method but simpler in comparison to using the value 1.8 by hand. Please note that using this method may require subtracting a degree or two for a completely accurate conversion.

Example: What is the temperature of Fahrenheit from 10 degrees Celsius?

((10*C x 2) - 1 ) + 32 = ?F

((20)-1)) + 32 = ?F

19 + 32 =?F

51=?F

You find that 10 degrees Celsius is roughly equal to 51 degrees Fahrenheit.

4. Reference Recipes with Similar Conversions

Consult other recipes that contain similar temperature units. Recipes often account for differences in temperature units, so they list the degrees in Fahrenheit and Celsius, which provides a method that's free of any mathematics.

Fun Fact

Parity is a single point at which the Celsius scale and Fahrenheit scale are equivalent, occurring at -40 degrees. In other words, -40°F equals -40°C!

Here’s the math to prove it:

(-40 x 1.8) + 32

-72 + 32

= -40°

And that’s it—all you need to know about Celsius, Fahrenheit, and switching between the two. Of course, if you have a calculator on hand, we always recommend using the formulas to get an exact conversion value.