What Is a Temperature Converter?
A temperature converter expresses one reading on another scale. Use it to translate a weather forecast, follow a recipe in different units or check a science calculation. This tool supports Celsius, Fahrenheit and Kelvin, with optional Rankine, and keeps conversion entirely in your browser.
How to use the temperature converter
- Start with the default 32 °F to Celsius, or enter your own reading.
- Choose the source and target units. A source-unit change converts the current reading; type a new value to replace it.
- Choose decimal precision. The answer and equivalent readings update instantly.
- Use Swap units to reverse the conversion while retaining the same temperature.
- Open the calculation steps or copy, print and download the result. For a rise or fall, choose Temperature Difference first.
The input accepts decimal commas such as 12,5, standard thousands grouping such as 1,234, and scientific notation such as 1e6. A lone minus sign or unfinished exponent stays editable while the result waits for a complete number. Use Change sign if your phone keyboard has no minus key.
Precision rounds the display only, with half-way values rounded away from zero. Results with magnitude at least 10¹⁵ use scientific notation; the precision then applies to its mantissa. Swapped inputs can be shortened to twelve decimals while the complete value remains available internally.
How to Convert Fahrenheit to Celsius and Back
Fahrenheit to Celsius formula
°C = (°F − 32) × 5/9
First remove the Fahrenheit zero-point offset, then change the degree size. For 68 °F, subtract 32 to get 36, then multiply by 5/9 to get 20 °C. The same method works for negative readings above absolute zero.
Celsius to Fahrenheit formula
°F = °C × 9/5 + 32
Reverse the order: scale the Celsius reading, then add the offset. For 30 °C, calculate 30 × 9/5 = 54, then 54 + 32 = 86 °F. The exact 9/5 factor explains why a Celsius degree spans a larger interval than a Fahrenheit degree.
Celsius, Fahrenheit and Kelvin Conversion Formulas
Celsius to Kelvin conversion
K = °C + 273.15. Add the exact offset: 25 °C + 273.15 = 298.15 K.
Kelvin to Celsius conversion
°C = K − 273.15. Subtract the offset: 280 K − 273.15 = 6.85 °C.
Fahrenheit to Kelvin conversion
K = (°F − 32) × 5/9 + 273.15. Convert to Celsius and then shift to Kelvin, without rounding between those operations. For example, 50 °F becomes 10 °C, then 283.15 K.
Kelvin to Fahrenheit conversion
°F = (K − 273.15) × 9/5 + 32. For 283.15 K, the Celsius intermediate is 10, giving 50 °F.
Optional Rankine conversions
Rankine uses an absolute zero point with Fahrenheit-sized degrees: °R = K × 9/5, K = °R × 5/9, and °R = °F + 459.67. Enable it under Advanced options to include it in selectors and reports.
Celsius, Fahrenheit and Kelvin Compared
Celsius and Fahrenheit use different degree sizes and zero points. Celsius is common in everyday metric measurements; Fahrenheit is used for many everyday readings in the United States. Kelvin is the SI unit of thermodynamic temperature. A Celsius degree and a kelvin have the same interval size, but their zero points differ.
Use the converter for a cooking or oven temperature, but treat the answer as a unit conversion. It does not adjust cooking time, oven calibration or fan settings. Weather readings also convert directly; a temperature range or change needs the difference mode.
What Is Absolute Zero?
0 K = −273.15 °C = −459.67 °F = 0 °R. This is the lower limit used for ordinary absolute temperatures in this tool. Lower inputs produce a clear error rather than being silently changed to zero.
Why is −40 the same in Celsius and Fahrenheit?
Set the two numerical readings equal: x = 9x/5 + 32. Rearranging gives −4x/5 = 32, so x = −40. The readings coincide at that point even though the degree sizes remain different.
Temperature Difference vs Absolute Temperature
An absolute reading is a position on a scale; a difference measures how far two readings are apart. Offsets cancel when subtracting readings, so an interval uses only a scale factor.
Δ°F = Δ°C × 9/5; Δ°C = Δ°F × 5/9; ΔK = Δ°C. A reading of 10 °C corresponds to 50 °F, but a rise of 10 °C corresponds to a rise of 18 °F. A fall of 10 K is a change of −10 K, equivalent to −18 °F.
Switching modes reinterprets the displayed input as a reading or a signed change. The Δ marker identifies interval outputs. The absolute-zero limit does not apply to a change.
Common Temperature Conversion Examples
For quick reference, 0 °C converts to 32 °F, and the reverse gives 32 °F = 0 °C. A boiling-water reference of 100 °C converts to 212 °F. The chart above includes the 37 °C / 98.6 °F reference as well as everyday weather readings.
For a repeating decimal example, 100 °F ≈ 37.78 °C at two decimal places. For a Kelvin example, 300 K = 26.85 °C. Increase precision in the calculator to see how rounding changes the displayed answer.
Frequently Asked Questions
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit reading, then multiply by 5/9. Select Fahrenheit as the source and Celsius as the target to calculate it instantly.
What is the Fahrenheit to Celsius formula?
C = (F − 32) × 5/9. Keep the complete intermediate value and round only the final displayed answer.
How do I convert Celsius to Fahrenheit?
Multiply the Celsius reading by 9/5, then add 32: F = C × 9/5 + 32.
How many Fahrenheit degrees is 25°C?
A reading of 25 °C equals 77 °F. A temperature change of 25 °C instead equals a change of 45 °F.
What is 100°F in Celsius?
100 °F is approximately 37.78 °C at two decimal places. Choose four decimals for 37.7778 °C.
What is 98.6°F in Celsius?
98.6 °F equals 37 °C. This is a conversion of a reference reading, not a threshold for interpreting an individual’s health.
What is 32°F in Celsius?
32 °F equals 0 °C. The reverse conversion gives 0 °C = 32 °F.
How do I convert Kelvin to Celsius?
Subtract 273.15 from the Kelvin value. For example, 273.15 K is 0 °C.
What is 300 Kelvin in Celsius?
300 K equals 26.85 °C: subtract the exact 273.15 offset.
Why does Kelvin not use a degree symbol?
The SI unit is named the kelvin, with the symbol K. Write 300 K, rather than adding a degree symbol. Celsius and Fahrenheit retain °C and °F.
What is absolute zero?
Absolute zero is 0 K, equivalent to −273.15 °C, −459.67 °F and 0 °R. It is the lower boundary for the ordinary thermodynamic readings supported here.
Can a temperature be negative in Kelvin?
This converter rejects negative absolute Kelvin readings. Negative changes in kelvins are valid in Temperature Difference mode because they describe a decrease.
How do I convert a temperature difference?
Use only degree sizes: multiply a Celsius or Kelvin change by 9/5 for a Fahrenheit or Rankine change. Reverse that conversion with 5/9. Never add 32 to a difference.
Is centigrade the same scale as Celsius?
In everyday temperature conversion, centigrade is the older name used for Celsius. A centigrade-to-Fahrenheit calculation therefore uses the Celsius-to-Fahrenheit formula.
Does water always boil at 100°C?
No. The familiar 100 °C reference assumes standard atmospheric pressure. The boiling point changes with pressure, including at different altitudes.
Sources and Related Conversion Tools
Temperature relationships and symbols follow NIST’s SI Units: Temperature. The NIST Guide to the SI, Appendix B.9 also distinguishes absolute readings from temperature intervals and lists Rankine relationships.
Working with temperature and humidity? Use our Dew Point Calculator to estimate when condensation may occur.
Explore more tools in Unit Conversions.