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Quick reference
Celsius (°C) to Fahrenheit (°F)
-40 °C
= -40 °F
-20 °C
= -4 °F
0 °C
= 32 °F
10 °C
= 50 °F
20 °C
= 68 °F
25 °C
= 77 °F
30 °C
= 86 °F
37 °C
= 98.6 °F
100 °C
= 212 °F
Temperature conversion formulas
°F = °C × 9/5 + 32 °C = (°F − 32) × 5/9 K = °C + 273.15
0°C = 32°F = 273.15 K
Unlike other units, temperature scales have different zero points, so conversion requires addition/subtraction — not just multiplication.
Units in this category
Celsius °C
Water freezes at 0°C and boils at 100°C. Used worldwide for weather, cooking, and science.
Fahrenheit °F
Water freezes at 32°F and boils at 212°F. Used in the US for weather and cooking.
Kelvin K
Starts at absolute zero (0 K = −273.15°C). Used in physics and engineering. No negative values.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (or 1.8), then add 32. For example, 25°C = 25 × 1.8 + 32 = 77°F.
What is absolute zero?
Absolute zero is 0 Kelvin (−273.15°C or −459.67°F). It is the theoretical lowest possible temperature where all molecular motion stops.
At what temperature are Celsius and Fahrenheit equal?
−40. Both scales read −40 at the same point: −40°C = −40°F.
Why does the US use Fahrenheit?
Fahrenheit was adopted early in US history and persisted through tradition. The finer degree increments (180 between freezing and boiling vs 100 in Celsius) can feel more precise for weather.
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