Unit conversion
Celsius to Fahrenheit: Formula, Chart, and Quick Conversion
Convert °C to °F with the exact formula (×9/5+32), mental math tricks, and a reference table. Free Celsius to Fahrenheit converter linked.
6 min read · Published 2026-05-21
Weather apps, ovens, and travel often mix Celsius (°C) and Fahrenheit (°F). The US and a few other regions use Fahrenheit; most of the world uses Celsius. This guide gives the exact formula, quick estimates, a reference chart, and our Celsius to Fahrenheit converter for any value.
The exact Celsius to Fahrenheit formula
To convert Celsius to Fahrenheit:
°F = (°C × 9/5) + 32
You can also write °F = (°C × 1.8) + 32 because 9 ÷ 5 = 1.8.
Example: 25 °C to °F
(25 × 9/5) + 32 = 45 + 32 = 77 °F
Example: 0 °C (freezing water)
(0 × 9/5) + 32 = 32 °F
Example: 100 °C (boiling water at sea level)
(100 × 9/5) + 32 = 180 + 32 = 212 °F
Need the reverse? Use Fahrenheit to Celsius or multiply mentally: °C = (°F − 32) × 5/9.
Quick mental math
Double-and-add method (rough)
- Multiply °C by 2
- Add 30 (close for everyday temps; exact offset is 32)
20 °C: 20 × 2 = 40, + 30 ≈ 70 °F (exact: 68 °F)
For weather bands
- Cool day (~10 °C): about 50 °F
- Room (~20 °C): about 68 °F
- Hot day (~30 °C): about 86 °F
- Very hot (~40 °C): about 104 °F
Where each scale is common
| Celsius | Fahrenheit | Context |
|---|---|---|
| −40 | −40 | Same number (rare cold) |
| 0 | 32 | Water freezes |
| 10 | 50 | Cool autumn day |
| 20 | 68 | Comfortable room |
| 25 | 77 | Warm summer day |
| 30 | 86 | Hot afternoon |
| 37 | 98.6 | Body temperature (approx.) |
| 100 | 212 | Water boils (sea level) |
Celsius vs Fahrenheit — why two scales?
Celsius ties 0° to water freezing and 100° to boiling at standard pressure—handy for science. Fahrenheit uses a different zero and smaller degrees, so whole numbers for daily weather often sit in a familiar 0–100 band in the US. Neither is “wrong”; you just need a reliable switch between them.
Cooking and oven temperatures
Recipe sites may list 180 °C for baking. Using the formula:
(180 × 9/5) + 32 = 356 °F (often rounded to 350 °F on dial ovens)
Always confirm whether the recipe means fan/convection or conventional heat—conversion is only the number, not oven mode.
Use the free online converter
For decimals, odd values, or homework:
- Open Celsius to Fahrenheit
- Enter °C
- Read °F instantly in your browser
The tool also supports other temperature units on the same page family (Kelvin, Rankine, etc.) via the site’s temperature category.
Common mistakes
- Forgetting to add 32 after multiplying
- Multiplying by 5/9 when you meant 9/5 (that is °F → °C)
- Rounding too early in multi-step science problems
Bottom line
°F = (°C × 9/5) + 32 is the formula to remember. For speed, double °C and add 30 is a workable weather estimate. For exact values, use the Celsius to Fahrenheit converter.
More length and distance conversions? See kilometers to miles.