How to Convert Celsius to Fahrenheit (Formula + Quick Trick)
Reading a weather forecast or recipe in the other temperature scale is confusing until you know the conversion. This guide gives you the exact Celsius-to-Fahrenheit formula, a quick mental shortcut for a close estimate, and the reference points worth memorizing — plus a free converter for exact answers.
🌡️ Try the Unit Converter now — freeOpen →Temperature scales differ by country, so travelers, cooks and anyone reading international content constantly need to convert. Knowing the formula and a quick estimate means you're never lost, whether it's the weather, an oven, or a fever.
The exact formula
To convert Celsius to Fahrenheit: multiply by 9/5 (or 1.8) and add 32. So 20°C = 20 × 1.8 + 32 = 68°F. To go back, Fahrenheit to Celsius: subtract 32, then multiply by 5/9. So 68°F = (68 − 32) × 5/9 = 20°C.
The key is the two steps — a scale factor and the +32 offset. The offset is what people forget, and it's why you can't just multiply. A converter handles it automatically for exact results.
A quick estimate and reference points
For a fast mental estimate: double the Celsius and add 30. 20°C → 20 × 2 + 30 = 70 (actual 68) — close enough for weather. It's slightly off because the real factor is 1.8, not 2, but it's handy on the fly.
Worth memorizing: 0°C = 32°F (freezing), 37°C ≈ 98.6°F (body temperature), 100°C = 212°F (boiling), and −40°C = −40°F (where the scales meet).
Step-by-step
Common mistakes to avoid
Pro tips
Frequently asked questions
What's the Celsius to Fahrenheit formula?
Multiply by 9/5 (1.8) and add 32. For example, 25°C × 1.8 + 32 = 77°F.
Is there a quick mental trick?
Double the Celsius and add 30 for a close estimate — good enough for weather, though slightly high.
What is 20°C in Fahrenheit?
68°F. (20 × 1.8 + 32 = 68.)
Why add 32?
The two scales have different zero points, so temperature needs an offset (+32), not just a multiplication.
Is the converter free?
Yes — free with no sign-up, giving exact conversions instantly.
Celsius to Fahrenheit is ×1.8 then +32 — never forget the offset. For a quick guess, double and add 30; for precision, use the converter. Memorize a few reference points and you'll read any temperature confidently, in either scale.