Celsius to Fahrenheit, Kelvin & More Converter
Enter a temperature in Celsius to convert it to Fahrenheit, Kelvin, Rankine, Newton, Delisle, Réaumur, and Rømer.
Temperature Scale Conversion Tool
Celsius Temperature Conversion Formula
Where:
- \(C\) — temperature in degrees Celsius (°C).
- \(F\), \(K\), and \(Ra\) — temperatures in degrees Fahrenheit (°F), kelvin (K), and degrees Rankine (°R).
- \(N\), \(D\), \(Re\), and \(Ro\) — temperatures in degrees Newton (°N), Delisle (°De), Réaumur (°Re), and Rømer (°Rø).
Each equation converts the same Celsius temperature to a different scale. The Newton and Rømer expressions use the decimal divisors in the calculator; their results may differ very slightly from calculations using exact fractional conversion factors.
Celsius Temperature Conversion – Calculation Example
Example: Convert the calculator’s default temperature of 25 °C to all seven scales.
\[\begin{aligned}
F &= 1.8(25)+32=77\ ^\circ\mathrm{F} \\
K &= 25+273.15=298.15\ \mathrm{K} \\
Ra &= 1.8(25)+491.67=536.67\ ^\circ\mathrm{R} \\
N &= 25/3.03030303\approx8.25\ ^\circ\mathrm{N} \\
D &= 1.5(100-25)=112.5\ ^\circ\mathrm{De} \\
Re &= 0.8(25)=20\ ^\circ\mathrm{Re} \\
Ro &= 25/1.9047619+7.5\approx20.625\ ^\circ\mathrm{R\o}
\end{aligned}\]
Result: 25 °C equals 77 °F, 298.15 K, 536.67 °R, approximately 8.25 °N, 112.5 °De, 20 °Re, and 20.625 °Rø. The calculator may round displayed results.
How to use the calculator
- Enter a number in the Temperature in Celsius field. The default is 25 °C; you can replace it with a positive, zero, negative, or decimal value.
- Read the results labeled Fahrenheit, Kelvin, Rankine, Newton, Delisle, Reaumur, and Rømer. All seven results refer to the same temperature you entered.
- Check the unit beside each result before copying it. For example, kelvin uses K without a degree sign, while Rankine uses °R.
What Celsius conversion results mean
A temperature scale assigns a number to a thermal state. The scales in this calculator use different zero points, different-sized degrees, or both. Conversion changes the number and unit, not the temperature itself. For example, 25 °C, 77 °F, and 298.15 K describe the same temperature.
Fahrenheit is commonly used for weather and everyday temperatures in the United States. Kelvin is the thermodynamic temperature scale used widely in science: a change of 1 °C has the same size as a change of 1 K, but 0 K corresponds to −273.15 °C. Rankine also starts at absolute zero, but its degree has the same size as a Fahrenheit degree. If you need to start with another unit, use the Fahrenheit converter or Kelvin converter.
Newton, Delisle, Réaumur, and Rømer are historical scales. Their numbers can look unfamiliar even for ordinary temperatures. Delisle runs in the opposite direction from Celsius: as Celsius rises, the Delisle reading falls. Rømer starts at 7.5 °Rø when Celsius is 0 °C. Keep the scale name and unit with any result so it is not mistaken for a reading on another scale.
Reference points and practical limits
Two useful checks are the freezing and boiling points of water at standard atmospheric pressure. The table shows their conventional scale values; an actual boiling point changes with pressure.
| Reference point | Celsius | Fahrenheit | Kelvin | Delisle |
|---|---|---|---|---|
| Water freezes | 0 °C | 32 °F | 273.15 K | 150 °De |
| Water boils | 100 °C | 212 °F | 373.15 K | 0 °De |
Enter an absolute temperature, not a temperature change. For instance, a rise of 10 °C is a rise of 18 °F, but converting the temperature 10 °C gives 50 °F because the Fahrenheit formula also adds 32. Kelvin likewise adds 273.15 when converting a temperature, not when converting a difference.
The calculator applies its equations to the number entered, even below −273.15 °C. Such an entry produces negative kelvin and Rankine values, which do not represent physically possible thermodynamic temperatures. Results may also be rounded for display, so retain appropriate precision if you use a conversion in further calculations.
If your starting value is in Rankine rather than Celsius, use the Rankine converter to convert in the other direction.
Frequently Asked Questions
How can I estimate Celsius to Fahrenheit in my head?
Double the Celsius number, subtract 10% of that doubled number, then add 32. This approximates multiplying by 1.8. For 20 °C, double to get 40, subtract 4, and add 32 to get 68 °F. It works for negative temperatures too, provided you keep track of the signs.
How do I convert Fahrenheit back to Celsius?
Subtract 32 from the Fahrenheit temperature, then multiply by 5/9: \(C=(F-32)\times 5/9\). For example, 86 °F becomes \((86-32)\times 5/9=30\) °C. Subtract before multiplying; reversing those steps is a common source of incorrect answers.
What is a typical room temperature in Celsius?
About 20–22 °C (68–72 °F) is a common indoor comfort range, but there is no single correct room temperature. Preferences vary with clothing, activity, humidity, and the season. A room described as “room temperature” in an experiment or product instruction may use a different specified range, so check its definition.
At what temperature are Celsius and Fahrenheit the same?
Both scales read −40 at the same temperature: −40 °C equals −40 °F. This is their only shared numerical reading because the scales have different zero points and degree sizes. You can check it by converting −40 °C: multiplying by 1.8 gives −72, and adding 32 gives −40.
Can a Delisle temperature be negative?
Yes. The Delisle scale assigns 0 °De to water’s conventional boiling point of 100 °C and decreases as Celsius increases. A temperature above 100 °C therefore has a negative Delisle reading; for example, 120 °C is −30 °De. Negative °De does not mean the temperature is below freezing.
Are Celsius and centigrade the same thing?
In everyday temperature conversions, “centigrade” means the Celsius scale, so a reading of 20 degrees centigrade is 20 °C. Celsius is the standard modern name. The older term refers to the 100-degree span between the conventional freezing and boiling points of water at standard atmospheric pressure.
Is 20 °C twice as hot as 10 °C?
No. Celsius has an offset from absolute zero, so ratios of Celsius readings do not express ratios of thermodynamic temperature. In kelvin, 20 °C is 293.15 K and 10 °C is 283.15 K—only about 3.5% apart as absolute temperatures. How hot something feels also depends on factors beyond its temperature.