Celsius to Fahrenheit and Fahrenheit to Celsius
°F = °C × 9/5 + 32
°C = (°F − 32) × 5/9
Temperature Converter: Celsius to Fahrenheit, Kelvin & More
Convert a temperature
Enter one number in any field. A decimal point or decimal comma is accepted; do not use thousands separators.
Kelvin cannot be below 0 K (−273.15 °C or −459.67 °F).
Advanced scales: Rankine and Réaumur
Conversion result
Enter a temperature to see the converted value and worked calculation here.
Formula:
Calculation:
Celsius
Fahrenheit
Kelvin
Rankine
Réaumur
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Common temperature conversion table
Absolute zero and the conversions between columns are exact; everyday reference temperatures are approximate. Water’s boiling point depends on atmospheric pressure.
| Reference | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Celsius/Fahrenheit crossover | −40 | −40 | 233.15 |
| Typical freezer | −18 | −0.4 | 255.15 |
| Water freezes | 0 | 32 | 273.15 |
| Cool day | 10 | 50 | 283.15 |
| Room temperature | 20 | 68 | 293.15 |
| Warm day | 30 | 86 | 303.15 |
| Typical body temperature | 37 | 98.6 | 310.15 |
| Hot day | 40 | 104 | 313.15 |
| Water boils at standard atmosphere | 100 | 212 | 373.15 |
Oven temperature conversion table
| Oven description | Celsius (°C) | Fahrenheit (°F) |
|---|---|---|
| Very slow | 120 | 250 |
| Slow | 150 | 300 |
| Moderate | 180 | 356 |
| Moderately hot | 190 | 374 |
| Hot | 200 | 392 |
| Very hot | 230 | 446 |
Oven dials commonly round these calculated values, so recipes may show nearby settings such as 350 °F for 180 °C.
Temperature conversion formulas
Celsius to Kelvin and Kelvin to Celsius
K = °C + 273.15
°C = K − 273.15
Fahrenheit to Kelvin and Kelvin to Fahrenheit
K = (°F − 32) × 5/9 + 273.15
°F = (K − 273.15) × 9/5 + 32
Kelvin to Rankine and Rankine to Kelvin
°Ra = K × 9/5
K = °Ra × 5/9
Celsius to Réaumur and Réaumur to Celsius
°Ré = °C × 4/5
°C = °Ré × 5/4
Variables: °C is Celsius temperature, °F is Fahrenheit temperature, K is kelvin temperature, °Ra is Rankine temperature, and °Ré is Réaumur temperature.
Temperature values are not temperature differences
The formulas above convert an actual temperature, so their scale origins require the 32 and 273.15 offsets. For a temperature change or interval, do not use those offsets: Δ°F = Δ°C × 9/5, Δ°C = Δ°F × 5/9, ΔK = Δ°C, and Δ°Ra = Δ°F.
Understanding the temperature scales
Which scale should I use?
Celsius is common for weather and cooking in most countries; Fahrenheit is common for everyday temperatures in the United States. Kelvin is the SI unit used in science. Rankine is an absolute scale with Fahrenheit-sized intervals, while Réaumur is mainly of historical interest.
Why does Fahrenheit need an offset?
Celsius and Fahrenheit have different zero points as well as different interval sizes. The +32 or −32 aligns their zero points; the 9/5 or 5/9 factor adjusts the interval size.
Why is there no degree symbol for Kelvin?
The SI name is the kelvin and its symbol is K. BIPM records that “degree kelvin” and °K were replaced by kelvin and K, so the correct form is 273.15 K.
How do absolute and relative scales differ?
Kelvin and Rankine start at absolute zero. Celsius, Fahrenheit, and Réaumur use conventional reference points, so their readings can be negative. Absolute zero is the lower limit of thermodynamic temperature; it should not be described simply as the point where all molecular motion stops.
Why can water boil below 100 °C?
Boiling occurs when a liquid’s vapour pressure matches the surrounding pressure. Lower atmospheric pressure at higher altitude lowers water’s boiling point, while higher pressure raises it.
Calculation method and sources
Maintained and formula-reviewed by Starlight Robotics. Updated 15 July 2026.
The converter validates a complete numeric entry, normalizes a decimal comma to a decimal point, converts the source value through Celsius, and rounds only the displayed results to your selected precision.
Definitions and exact °C/°F/K relationships are checked against NIST SI temperature guidance. Kelvin name and symbol usage follows the BIPM history of the kelvin.
Temperature converter FAQs
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5, then add 32. For example, 25 °C × 9/5 + 32 = 77 °F.
What is 100 °F in Celsius?
100 °F is approximately 37.78 °C. The calculation is (100 − 32) × 5/9 = 37.777… °C.
What temperature is the same in Celsius and Fahrenheit?
−40 is the same on both scales: −40 °C = −40 °F.
Can Kelvin be negative?
Not for a thermodynamic temperature. The Kelvin scale starts at absolute zero, 0 K, equivalent to −273.15 °C and −459.67 °F. This converter rejects lower values.
Why does Kelvin not use a degree symbol?
The SI unit is named the kelvin and its symbol is K, not °K. Write 300 K, while Celsius and Fahrenheit use °C and °F.
How do temperature differences convert?
For differences, 1 °C equals 1 K and 1 °C equals 1.8 °F or 1.8 °Ra. Do not add 32 or 273.15 when converting a temperature difference.
Are freezing and boiling values exact at every altitude?
No. Water’s phase-change temperatures depend on pressure and purity. The familiar 0 °C freezing and 100 °C boiling values are reference values; boiling is about 100 °C at standard atmospheric pressure and is lower at higher altitudes.