Fahrenheit to Celsius, Kelvin & More Converter
Enter a temperature in Fahrenheit to see its equivalent in Celsius, Kelvin, Rankine, Newton, Delisle, Réaumur, and Rømer.
Fahrenheit Temperature Conversion Tool
Fahrenheit Temperature Conversion Formula
Where:
- \(F\) — temperature in degrees Fahrenheit (°F).
- \(C\) — temperature in degrees Celsius (°C).
- \(K\) — temperature in kelvin (K).
- \(Ra\), \(N\), \(De\), \(Re\), and \(Ro\) — temperatures in degrees Rankine (°R), Newton (°N), Delisle (°De), Réaumur (°Re), and Rømer (°Rø), respectively.
First convert Fahrenheit to Celsius, then use Celsius to calculate most of the other scales. Rankine can be calculated directly from Fahrenheit because both scales use equal-sized degrees.
Fahrenheit Temperature Conversion – Calculation Example
Example: Convert 77 °F, the calculator’s default value, to every available temperature scale.
Start with Celsius:
\[C=\frac{77-32}{1.8}=25\,^{\circ}\mathrm{C}\]
Use 25 °C to find the remaining values:
\[\begin{aligned}K&=25+273.15=298.15\,\mathrm{K} \\ Ra&=77+459.67=536.67\,^{\circ}\mathrm{R} \\ N&=0.33(25)=8.25\,^{\circ}\mathrm{N} \\ De&=1.5(100-25)=112.5\,^{\circ}\mathrm{De} \\ Re&=0.8(25)=20\,^{\circ}\mathrm{Re} \\ Ro&=0.525(25)+7.5=20.625\,^{\circ}\mathrm{Rø}\end{aligned}\]
Result: 77 °F equals 25 °C, 298.15 K, 536.67 °R, 8.25 °N, 112.5 °De, 20 °Re, and 20.625 °Rø. Displayed results may be rounded.
How to use the calculator
- Enter a number in the Temperature in Fahrenheit field. You can enter a negative value, a positive value, or a decimal.
- Read the converted temperatures in the Celsius, Kelvin, Rankine, Newton, Delisle, Reaumur, and Rømer results.
- Check the unit beside each result before copying it. Kelvin uses K, not °K; the other results use their respective degree symbols.
Understanding Fahrenheit and the other temperature scales
Fahrenheit is commonly used for weather and everyday temperatures in the United States. On this scale, water freezes at 32 °F and boils at 212 °F under standard atmospheric pressure. Celsius assigns those same reference temperatures 0 °C and 100 °C, so a change of 1 °C corresponds to a change of 1.8 °F. That is why Fahrenheit-to-Celsius conversion requires both subtracting 32 and dividing by 1.8.
Kelvin and Rankine are absolute temperature scales: their zero points correspond to absolute zero. Kelvin increments have the same size as Celsius degrees, while Rankine increments have the same size as Fahrenheit degrees. This makes 0 °C equal to 273.15 K and 32 °F equal to 491.67 °R. Kelvin is especially useful in scientific calculations, where an absolute temperature may be required rather than a value relative to water’s freezing point.
Newton, Delisle, Réaumur, and Rømer are less common temperature scales that may appear in historical sources or conversion exercises. Do not assume their numerical values rise in the same direction: Delisle runs downward as Celsius rises. For example, water’s freezing point is 150 °De, while its boiling point is 0 °De. A converted number is meaningful only when you keep its scale and unit attached.
Practical notes and limitations
These formulas convert temperature values, not temperature differences. To convert a change of 18 °F to Celsius degrees, divide by 1.8 to get a change of 10 °C; do not subtract 32. Likewise, a change of 1 °F is a change of 1 °R, even though the two scales have different zero points.
The calculator may round displayed results. If you need to carry a result into another calculation, keep enough decimal places to avoid accumulating rounding error. The conversion formulas describe the scales; they do not account for thermometer uncertainty, sensor calibration, or differences between a measured temperature and an exact reference value.
An ordinary temperature cannot be below absolute zero, which is −459.67 °F, 0 K, or 0 °R. The field may still accept a lower number and return mathematical conversions, but those results do not describe a physically attainable ordinary temperature.
Quick reference points
| Reference point | Fahrenheit | Celsius | Kelvin | Rankine |
|---|---|---|---|---|
| Absolute zero | −459.67 °F | −273.15 °C | 0 K | 0 °R |
| Water freezes | 32 °F | 0 °C | 273.15 K | 491.67 °R |
| Water boils | 212 °F | 100 °C | 373.15 K | 671.67 °R |
The water reference points assume standard atmospheric pressure. To start with another scale instead, use the Celsius converter, Kelvin converter, Rankine converter, or Delisle converter.
Frequently Asked Questions
How can I estimate Fahrenheit to Celsius in my head?
Subtract 30 from the Fahrenheit temperature, then divide by 2 for a quick estimate. For 70 °F, that gives about 20 °C; the exact result is about 21.1 °C. This shortcut works reasonably well for everyday weather temperatures, but use the exact conversion for scientific or medical measurements.
What is 100 °F in Celsius and Kelvin?
100 °F is approximately 37.78 °C or 310.93 K. It is warmer than typical room temperature and close to human body temperature, but the meaning of a 100 °F reading depends on what was measured. For a body-temperature reading, the measurement method and a person’s symptoms matter.
Is 98.6 °F always a normal body temperature?
No. Although 98.6 °F (37 °C) is a familiar reference value, healthy body temperature varies between people, throughout the day, and by measurement site. A single reading does not establish whether someone has a fever. If you are concerned about a temperature or symptoms, follow appropriate medical guidance.
At what temperature are Fahrenheit and Celsius the same?
The two scales have the same numerical value at −40 degrees: −40 °F equals −40 °C. You can find this by setting the Fahrenheit and Celsius numbers equal in the conversion equation and solving for that number. This is the only point where their numerical readings coincide.
How do I convert Celsius back to Fahrenheit?
Multiply the Celsius value by 1.8, then add 32: \(F=1.8C+32\). For example, 20 °C becomes 68 °F. This reverses a Fahrenheit-to-Celsius conversion, though a value copied from a rounded calculator result may not return precisely to the original Fahrenheit input.
Can I convert Fahrenheit to kelvin by adding 273.15?
No. Adding 273.15 converts Celsius to kelvin, not Fahrenheit to kelvin. First account for Fahrenheit’s different zero point and degree size: \(K=(F-32)\times 5/9+273.15\). For example, 32 °F is 273.15 K, whereas simply adding 273.15 to 32 would give the wrong result.
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