Convert Celsius to Fahrenheit
Convert °C to °F for US weather forecasts, oven temperatures and fever readings. Type a Celsius value to see the matching Fahrenheit reading.
1 °C = 33.8 °F
To convert Celsius to Fahrenheit, multiply by 9/5 and add 32: °F = (°C × 1.8) + 32. So 20 °C = 68 °F and 100 °C = 212 °F. Temperature is unlike length or mass because the two scales have different zero points as well as different degree sizes, which is why an offset is required and why a simple multiplication gives the wrong answer. A good mental shortcut is to double and add 30, which is within two degrees across normal weather: 22 °C gives 74 against the true 71.6. Worth memorising are the anchors — 0 °C is 32 °F, 10 °C is 50 °F, 20 °C is 68 °F, 30 °C is 86 °F, and body temperature 37 °C is 98.6 °F. The scales cross at −40, where both read the same number. Oven temperatures are the common domestic use, and 180 °C is 356 °F, which recipes round to 350 °F.
Quick reference: celsius to fahrenheit
| Celsius | Fahrenheit |
|---|---|
| -40 | −40 °F (scales meet) |
| 0 | 32 °F (freezing) |
| 10 | 50 °F |
| 20 | 68 °F (room temp) |
| 30 | 86 °F |
| 37 | 98.6 °F (body temp) |
| 38 | 100.4 °F (fever) |
| 100 | 212 °F (water boils) |
| 180 | 356 °F (oven) |
How do you convert celsius to fahrenheit?
Formula: °F = (°C × 9/5) + 32 • A 20 °C room → (20 × 1.8) + 32 = 68 °F, the middle of the usual comfort band. • A 37 °C body temperature → (37 × 1.8) + 32 = 98.6 °F, the familiar normal reading. • A 180 °C oven → (180 × 1.8) + 32 = 356 °F, which US recipes round to 350 °F. • The crossover point: −40 °C = −40 °F, the single temperature where both scales read the same.
When and why people use celsius to fahrenheit
Weather is the everyday case. The US, its territories and a small number of other places report in Fahrenheit while the rest of the world uses Celsius, so anyone travelling, reading foreign forecasts or comparing climate data converts constantly. A useful anchor set is 0 °C = 32 °F for freezing, 10 °C = 50 °F for a cool day, 20 °C = 68 °F for mild, and 30 °C = 86 °F for hot. Cooking is the second and the one where errors are most visible. European recipes give oven temperatures in Celsius and US ovens are marked in Fahrenheit, and the standard settings do not map onto round numbers in the other system — 180 °C is 356 °F, conventionally rounded to 350 °F. Medicine is the third. A fever threshold of 38 °C is 100.4 °F, a figure that appears in clinical guidance worldwide precisely because it is the exact conversion rather than a rounded one.
Common mistakes to watch for when converting celsius to fahrenheit
The most common error is forgetting the offset and simply multiplying by 1.8, which puts every result 32 degrees too low. The second is applying the conversion to a temperature difference rather than a temperature. If a thermostat is raised by 5 °C, the change is 9 °F, not 41 °F — for differences you use only the 1.8 factor and drop the offset entirely. Third, oven conversions are complicated by fan-assisted settings: a fan oven is typically set 20 °C lower than a conventional one for the same result, so a recipe specifying 180 °C conventional means 160 °C fan, or about 320 °F, before the Fahrenheit conversion is even applied. Finally, gas marks are a third scale again, with gas mark 4 corresponding to roughly 180 °C.
How to estimate celsius to fahrenheit in your head
Double the Celsius figure, subtract a tenth of that doubled number, then add 32. For 20 °C: double is 40, minus 4 is 36, plus 32 gives 68 °F — exactly right. This works because doubling and removing a tenth is precisely multiplying by 1.8. The cruder 'double it and add 30' is popular and is accurate only near 10 °C. At 20 °C it gives 70 instead of 68, and at 35 °C it gives 100 instead of 95 — a five-degree error in the range where the difference actually matters. Weather anchors worth memorising: 0 °C = 32 °F, 10 °C = 50 °F, 16 °C = 61 °F, 20 °C = 68 °F, 25 °C = 77 °F, 30 °C = 86 °F, 35 °C = 95 °F. Notice 16 and 61 — the digits reverse, which makes it an easy one to recall.
Celsius to Fahrenheit FAQ
What is the formula?
- °F = (°C × 9/5) + 32. The multiplication handles the different degree size and the +32 handles the different zero point.
What is 20 °C in Fahrenheit?
- 68 °F — the middle of the typical indoor comfort range.
Why can't I just multiply by 1.8?
- Because the scales have different zero points. Without adding 32 every answer is 32 degrees too low.
How do I convert a temperature change?
- Use only the 1.8 factor and omit the offset. A rise of 5 °C is a rise of 9 °F.
Is there a temperature where both scales agree?
- Yes, −40. It is the only point where °C and °F give the same number.
What oven temperature is 180 °C?
- 356 °F exactly, which US recipes normally round to 350 °F.
What about fan ovens?
- A fan oven usually runs 20 °C lower for the same result, so 180 °C conventional is about 160 °C fan before converting.
Is my input stored?
- No. The arithmetic runs in your browser and nothing is transmitted.
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Sources: BIPM SI brochure on the kelvin and derived temperature scales; NIST Special Publication 811; WHO and CDC clinical guidance on fever thresholds (38 °C / 100.4 °F).