Guide
How to use Celsius to Fahrenheit Converter
Start with the working tool above. The notes below explain the inputs, method, limitations and checks that matter for this specific task.
- 1. Type in the Celsius box for Fahrenheit and Kelvin.
- 2. Or type in the Fahrenheit box to convert back.
- 3. Use swap to flip direction without retyping.
- 4. Check the chart below for weather, body and oven temperatures.
- 5. Use Reset to clear both boxes.
How it works
The formula is °F = °C × 9/5 + 32, where °C is the Celsius temperature: multiply by 9, divide by 5 (or multiply by 1.8), then add 32. The reverse is °C = (°F − 32) × 5/9. Kelvin adds one step: K = °C + 273.15. The scales meet at exactly one point, −40 on both. Water freezes at 0°C = 32°F and boils at 100°C = 212°F — hence the +32 offset.
Worked examples
30°C to Fahrenheit (hot summer day)
30 × 9/5 + 32 = 54 + 32 = 86°F. A forecast of 30°C means 86°F — hot weather, not the mild day the number 30 suggests to a Fahrenheit reader.
38°C to Fahrenheit (fever range)
38 × 9/5 + 32 = 68.4 + 32 = 100.4°F — the figure most health guidance uses as the fever threshold, and one of the most searched conversions.
Reverse: 98.6°F to Celsius
(98.6 − 32) × 5/9 = 66.6 × 5/9 = 37°C. The classic normal body temperature of 98.6°F is exactly 37°C.
When this tool is useful
- Reading a forecast from a country using the other scale
- Converting a body temperature reading
- Setting an oven for a Celsius recipe
- Understanding temperatures when travelling
- School science and Kelvin for physics problems
How to Change Fahrenheit into Celsius
To change Fahrenheit into Celsius, reverse the formula: subtract 32, then multiply by 5/9. Written out: °C = (°F − 32) × 5/9. Room temperature: (68 − 32) × 5/9 = 36 × 5/9 = 20°C. Body temperature: (98.6 − 32) × 5/9 = 37°C. The order matters — the 32 is an offset between the scales' zero points, so it comes off before the multiplication.
- Step 1: start with the Fahrenheit temperature.
- Step 2: subtract 32.
- Step 3: multiply by 5, then divide by 9.
- Step 4: round sensibly — one decimal for body temperatures, whole numbers for weather.
Celsius to Fahrenheit conversion chart
The temperatures people convert most often, written out in full — no clicking or calculating required.
| Celsius (°C) | Fahrenheit (°F) | Commonly used for |
|---|---|---|
| −40 | −40 | Where the scales agree |
| 0 | 32 | Water freezes |
| 10 | 50 | A cool day |
| 15 | 59 | Mild spring day |
| 20 | 68 | Room temperature |
| 25 | 77 | A warm day |
| 30 | 86 | Hot summer day |
| 36 | 96.8 | Low-normal body temperature |
| 37 | 98.6 | Normal body temperature |
| 38 | 100.4 | Fever threshold |
| 40 | 104 | High fever |
| 50 | 122 | Hot water |
| 100 | 212 | Water boils at sea level |
| 180 | 356 | Baking temperature |
| 200 | 392 | Hot oven, roasting |
A note on body temperature and fever
Normal body temperature averages about 37°C (98.6°F) but varies by person, time of day and measurement site. Most health authorities treat 38°C (100.4°F) and above as a fever — which is why 36, 37 and 38°C are among the most converted temperatures anywhere. This converter gives the exact number; what to do about a fever is a medical question.
Common mistakes to avoid
- Forgetting the +32: 30°C × 1.8 alone gives 54, not 86°F — the offset is half the formula.
- Using 9/5 both ways; Fahrenheit to Celsius means subtract 32 first, then 5/9.
- Treating 37°C as a fever. It is normal body temperature (98.6°F); 38°C (100.4°F) is the fever threshold.
- Rounding mid-calculation, then wondering why a body temperature looks off — keep one decimal place until the end.
- Assuming the scales differ by a fixed amount; the gap grows with temperature because the degrees differ in size.
Frequently asked questions
What is 30 degrees Celsius in Fahrenheit?
30°C is 86°F: 30 × 9/5 + 32 = 86 — a hot summer day. The chart below lists more, including 15°C = 59°F and 20°C = 68°F.
Is 38°C a fever?
Yes — 38°C is 100.4°F, the threshold most medical guidance uses for fever in adults and children. Handling depends on age and symptoms, so follow clinician advice, not this page.
How do I convert Fahrenheit to Celsius quickly?
Subtract 32, then multiply by 5/9. For a rough estimate, subtract 32 and halve the result — within a couple of degrees for everyday weather.
Why do the two scales meet at −40?
Because the formulas cross there: −40 × 9/5 + 32 = −40. It is the one temperature reading the same on both scales — a handy check on your arithmetic.
What is 36°C in Fahrenheit — is it normal?
36°C is 96.8°F. Body temperature varies by person and time of day; 36–37°C (96.8–98.6°F) is generally normal, while sustained readings at or above 38°C indicate fever.
What temperature should I set for a 180°C recipe?
180°C is 356°F; most Fahrenheit ovens are set to 350°F for such recipes. European fan-oven figures are often 20°C below conventional settings, so check which the recipe means.
Bottom line
Multiply by 9/5 and add 32 going to Fahrenheit; subtract 32 and multiply by 5/9 coming back. For everyday weather, body and oven temperatures, the chart above is faster than a formula.
If the question changes shape, the closest neighbours are Unit Converter and Area Calculator — or browse everything under Converters.