The Formula
°F = °C × 9/5 + 32
Multiply the Celsius temperature by 9, divide by 5, add 32. Working the example above: 25 °C × 9/5 = 45, plus 32 = 77 °F. The two constants come from the scales’ anchor points: water freezes at 0 °C / 32 °F (hence the +32) and the Celsius degree is 9/5 the size of the Fahrenheit degree (hence the ratio).
The Mental Shortcut
For everyday weather, double the Celsius value and add 30: 20 °C → 70 °F (exact: 68). It’s perfectly exact at 10 °C = 50 °F and stays within ~2 °F between 0 and 30 °C — more than good enough for deciding what to wear. For cooking temperatures the shortcut drifts too far; use the converter above or the table.
Anchors Worth Memorizing
Cold winter day: 0 °C = 32 °F. Mild spring: 15 °C = 59 °F. Room temperature: 21 °C ≈ 70 °F. Hot day: 35 °C = 95 °F. Fever threshold: 38 °C = 100.4 °F. Moderate oven: 180 °C = 356 °F (recipes round to 350 °F). And the party trick: −40 is the same in both scales — the one point where they cross.
Frequently Asked Questions
Is 40 degrees Celsius hot?
Very — 40 °C is 104 °F, a dangerous heat-wave temperature. As body temperature it indicates high fever needing medical attention. (Meanwhile 40 °F is a chilly 4.4 °C.)
What is normal body temperature in Fahrenheit?
37 °C converts to 98.6 °F, the traditional figure. Modern measurements put typical body temperature slightly lower and varying by person and time of day — fever is generally flagged from 38 °C / 100.4 °F.
How do I convert oven temperatures for US recipes?
The common pairs: 160 °C ≈ 325 °F, 180 °C ≈ 350 °F, 200 °C ≈ 400 °F, 220 °C ≈ 425 °F. Recipes use rounded values on purpose — ovens aren’t precise instruments, so matching the nearest pair is standard practice.
Is this converter exact?
Yes — it applies the exact formula with no rounding shortcuts, entirely in your browser. The result shows up to 8 significant digits; round as your use case needs.