The formula
°F = (°C × 9 ÷ 5) + 32
°C = (°F − 32) × 5 ÷ 9
Unlike length or weight, temperature isn't a simple multiplication: the two scales have different zero points and step sizes, so you must apply the +32 offset.
Building intuition
| Reference | °C | °F |
|---|---|---|
| Water freezes | 0 | 32 |
| Cool room | 20 | 68 |
| Body temperature | 37 | 98.6 |
| Hot summer day | 35 | 95 |
| Water boils (sea level) | 100 | 212 |
| Oven (medium) | 180 | 356 |
−40° is the same in both
−40 °C and −40 °F are exactly equal — the only point where the two scales intersect. Above that, every Celsius rise of 5° equals 9° on the Fahrenheit scale.
Convert any temperature
Celsius (°C)
Fahrenheit (°F)
| Unit | 1 °C equals |
|---|---|
| Celsius (°C) | 1 |
| Fahrenheit (°F) | 33.8 |
| Kelvin (K) | 274.15 |
| Rankine (°R) | 493.47 |
What about Kelvin?
Kelvin uses the same step size as Celsius but starts at absolute zero — the theoretical minimum temperature where molecular motion stops. K = °C + 273.15. There is no degree symbol with Kelvin: write 300 K, not 300 °K.
Common mistake
Forgetting the +32 offset is the single most common conversion error. A weather forecast of 20 °C is not 20 °F — it's 68 °F, a comfortable spring day.
Frequently asked questions
Is there a simpler approximation?
Yes — double the Celsius value and add 30 for a rough estimate. 20 °C × 2 + 30 ≈ 70 °F (true value 68 °F).
Why does the US use Fahrenheit?
Historical inertia. The US adopted Fahrenheit through British colonial influence and never made the metric switch most of the world completed by the 1970s.
What temperature is a fever?
A body temperature above 38 °C (100.4 °F) is generally considered a fever in adults.
Related converters
The tools mentioned in this guide — one tap away.