Celsius to Fahrenheit: Formula, Chart, and Quick Trick

I Kept Getting This Wrong, and It Drove Me Nuts

So I was traveling for a job site visit a few years back — somewhere in Ontario — and the weather app on my phone said 22°C. I had absolutely no idea if that meant I should grab a jacket or not. I stood there in the hotel lobby like an idiot, Googling "22 Celsius in Fahrenheit" and then forgetting the answer by the time I got to the rental car. That happened more than once on that trip, honestly.

The thing is, the conversion formula isn't even hard. It's just that nobody ever taught it to me in a way that stuck. School made it feel like some chemistry-class thing, and my brain filed it under "stuff I'll never use." Except I use it all the time now — checking curing temperatures for concrete, reading spec sheets from European manufacturers, or just figuring out if 35°C means I should be worried about my crew working outside.

So yeah. Let's actually make this stick.

The Formula (It's One Line, I Promise)

That's literally it. Multiply by 9/5 (or 1.8 if decimals are easier for you), then add 32. And going the other way — Fahrenheit to Celsius — you just reverse it: subtract 32 first, then multiply by 5/9.

Let me walk through a real one.

Say it's 25°C outside. You multiply 25 by 1.8, which gives you 45. Then add 32. That's 77°F. Nice day — T-shirt weather. And the math took maybe four seconds once you know what to do.

Here's another: 0°C. Zero times 1.8 is zero, plus 32 equals 32°F. That's freezing. Which makes sense, because 0°C is literally the freezing point of water. And 32°F is the freezing point on the Fahrenheit side. So the formula checks out perfectly at that anchor point, which I find kind of satisfying.

One more, because I want to show where people mess up. Let's say you need to convert 100°C. That's 100 × 1.8 = 180, plus 32 = 212°F. Boiling point of water. If you accidentally add 32 first and then multiply, you'd get (100 + 32) × 1.8 = 237.6, which is just wrong. Order of operations matters here — multiply first, add second.

Use our

The Quick Reference Chart Everyone Needs on Their Phone

I screenshot charts like this and keep them in my photos. Don't judge me — it's faster than doing math when you're half awake.

That -40 row always blows people's minds. Both scales converge at -40. It's the one temperature where you don't need to convert anything, and also the one temperature where you really don't want to be outside.

The Quick Trick That Gets You Close Enough

Okay so the real formula uses 1.8, but here's a shortcut I picked up from a Canadian electrician I worked with: double it and add 30.

That's it. Double the Celsius number, add 30. It's not exact — it's off by a degree or two in most everyday ranges — but it's fast enough for "do I need a coat" decisions and rough mental estimates.

Let's test it:

• 20°C → double is 40, plus 30 = 70°F. (Actual: 68°F. Close enough!)
• 30°C → double is 60, plus 30 = 90°F. (Actual: 86°F. Off by 4, but you still know it's hot.)
• 10°C → double is 20, plus 30 = 50°F. (Actual: 50°F. Nailed it.)

The trick works best between about 0 and 30°C, which is where most weather happens anyway. Once you get into extreme temperatures — like above 40°C or below -10°C — the error grows and you're better off using the real formula or just plugging it into a

But for everyday stuff? Double and add 30. I've been using it for years.

Where This Actually Comes Up in Real Life

You might think temperature conversion is just a travel thing. It's not. I run into it constantly — and I bet you do too, even if you don't realize it.

Cooking is a big one. European recipes list oven temperatures in Celsius. So when a recipe says "preheat to 180°C," that's 356°F, which you'd round to 350°F on your oven dial. I've burned more than one thing because I didn't bother converting and just guessed. A

3D printing and electronics are another area — a lot of filament specs and solder temperatures come in Celsius. If your heat gun says 200°C and you need to know if that's going to melt something rated for 380°F, well, 200 × 1.8 + 32 = 392°F. Yeah, that's too hot.

And then there's the obvious one: weather. If you follow international news, check weather for a trip abroad, or just have a weather widget that defaults to metric for some reason, you need this conversion in your back pocket. I also use our

For other unit conversions you might need alongside this — like length or weight — check out the

And if math conversions in general stress you out, the