Temperature Converter
Celsius, Fahrenheit and Kelvin at once.
Reviewed by the Calculation Machine team · Updated 24 October 2026 · How we check our maths
Your values
ⓘ Live results
- Celsius
- 180 °C
- Fahrenheit
- 356 °F
- Kelvin
- 453.15 K
- Rankine
- 815.67 °R
Working
- 1°F = 180 × 9/5 + 32 = 356
Quick answer
To convert Celsius to Fahrenheit, multiply by 9/5 (1.8) and add 32. To go from Fahrenheit to Celsius, subtract 32 and multiply by 5/9. Kelvin is Celsius plus 273.15. For example, 180 °C is 356 °F and 453.15 K, and 98.6 °F is exactly 37 °C.
What the Temperature Converter does
Enter a temperature in Celsius, Fahrenheit or Kelvin and this converter shows it on all three scales plus Rankine, with the arithmetic written out so you can follow it. Typical uses are converting oven settings between US and European recipes, reading weather forecasts abroad, and switching to Kelvin for gas-law and thermodynamics problems.
Celsius and Fahrenheit both have arbitrary zero points, which is why the conversion needs an offset (the +32) as well as a scale factor. Kelvin and Rankine start at absolute zero, so they are the scales to use whenever a formula multiplies or divides by temperature — the ideal gas law is the classic case. Values below absolute zero (−273.15 °C or −459.67 °F) are not physical; the converter will still show a number, so treat a negative Kelvin result as a sign of a typo.
For cooking conversions of cups, spoons and weights, pair this page with the cooking measurement converter.
The formula
°F = °C × 9/5 + 32 °C = (°F − 32) × 5/9 K = °C + 273.15 °R = °F + 459.67
| Symbol | Meaning | Unit |
|---|---|---|
| °C | Degrees Celsius; water freezes at 0 and boils at 100 at standard pressure | °C |
| °F | Degrees Fahrenheit; water freezes at 32 and boils at 212 | °F |
| K | Kelvin, the SI unit; 0 K is absolute zero and a 1 K step equals a 1 °C step | K |
| °R | Degrees Rankine; absolute scale with Fahrenheit-sized steps, used in some US engineering | °R |
| 9/5 | Ratio of degree sizes: 180 Fahrenheit degrees span the same range as 100 Celsius degrees | — |
Since the 2019 SI redefinition, the kelvin is fixed by the Boltzmann constant, and Celsius is defined as kelvin minus 273.15 (BIPM SI Brochure). A temperature difference converts without the offset: a rise of 10 °C is a rise of 18 °F, not 50 °F. Use the full formula only for actual readings.
Worked examples
Body temperature from Fahrenheit
A US thermometer reads 98.6 °F and you want the Celsius value used in most other countries.
Inputs
- Temperature98.6
- FromFahrenheit
Result
- Celsius37 °C
- Fahrenheit98.6 °F
- Kelvin310.15 K
- Rankine558.27 °R
98.6 °F is exactly 37 °C. Normal adult body temperature varies by a degree or so through the day, so a single reading slightly off 37 °C is not unusual.
Where Celsius and Fahrenheit meet
Checking the one point where the two scales read the same number.
Inputs
- Temperature-40
- FromCelsius
Result
- Celsius-40 °C
- Fahrenheit-40 °F
- Kelvin233.15 K
- Rankine419.67 °R
−40 °C equals −40 °F, which is 233.15 K. Below this point a Fahrenheit reading is the lower number; above it, the Fahrenheit number is higher.
Lab temperature in Kelvin
A chemistry problem states a gas sample is at 300 K.
Inputs
- Temperature300
- FromKelvin
Result
- Celsius26.85 °C
- Fahrenheit80.33 °F
- Kelvin300 K
- Rankine540 °R
300 K is 26.85 °C or 80.33 °F — a warm room. Physics problems often round room temperature to 300 K for that reason.
Key temperatures on each scale
Boiling and freezing points are for pure water at standard sea-level pressure; water boils at lower temperatures at altitude.
| Reference point | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Celsius equals Fahrenheit | −40 | −40 | 233.15 |
| Water freezes | 0 | 32 | 273.15 |
| Comfortable room | 20 | 68 | 293.15 |
| Normal body temperature | 37 | 98.6 | 310.15 |
| Water boils (1 atm) | 100 | 212 | 373.15 |
| Moderate oven | 180 | 356 | 453.15 |
Oven temperatures: Celsius, Fahrenheit and gas mark
Recipes round oven settings, so the converted number rarely matches exactly. US recipes usually step in 25 °F, European ones in 10 °C. For a fan (convection) oven, many recipe writers suggest setting about 20 °C (roughly 25 °F) lower than a conventional oven.
| Gas mark | °F (recipe) | °C (recipe) | Exact °C |
|---|---|---|---|
| 2 | 300 | 150 | 148.9 |
| 4 | 350 | 180 | 176.7 |
| 5 | 375 | 190 | 190.6 |
| 6 | 400 | 200 | 204.4 |
| 7 | 425 | 220 | 218.3 |
Quick mental conversions
- Celsius to Fahrenheit, rough: double it and add 30. 20 °C → 70 °F (exact: 68 °F). The error grows at high temperatures, so do not use it for ovens.
- Fahrenheit to Celsius, rough: subtract 30 and halve. 80 °F → 25 °C (exact: 26.7 °C).
- Memory pairs: 10 °C = 50 °F, 16 °C ≈ 61 °F, 28 °C ≈ 82 °F, 30 °C = 86 °F.
- Changes in temperature: multiply a Celsius change by 1.8 to get the Fahrenheit change. A forecast that is 5 °C warmer is 9 °F warmer.
For how cold the air actually feels, use the wind chill calculator; for hot, humid days, the heat index calculator.
How to use the Temperature Converter
- 1Enter the temperature, including a minus sign for values below zero.
- 2Choose the scale it is in: Celsius, Fahrenheit or Kelvin.
- 3Read the result on the other scales; the working line shows the Fahrenheit formula with your numbers.
- 4For a temperature change rather than a reading, multiply by 1.8 (°C to °F) instead of using the converter.
Frequently asked questions
What is 350 °F in Celsius?
350 °F is 176.7 °C, which recipes round to 180 °C (or 160 °C in a fan oven). It is gas mark 4.
What is 0 °C in Fahrenheit?
0 °C is 32 °F, the freezing point of water. 0 °F is −17.8 °C.
How do you convert Kelvin to Celsius?
Subtract 273.15. For example, 300 K is 26.85 °C. Kelvin is written without a degree sign.
Can a temperature be below 0 Kelvin?
No. 0 K is absolute zero, the lowest temperature possible in classical thermodynamics. A negative Kelvin result from a conversion means the input was below −273.15 °C or −459.67 °F.
What is a fever in Celsius and Fahrenheit?
A temperature of 38 °C (100.4 °F) or higher is commonly treated as a fever in adults. Speak to a doctor or pharmacist if a fever is very high or lasts more than a few days.
References
- The International System of Units (SI Brochure) — Bureau International des Poids et Mesures (BIPM)
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI) — National Institute of Standards and Technology
About this calculator
- Built and reviewed by the Calculation Machine team · How we build and test calculators
- Last reviewed: October 24, 2026
- Report an error