How to use the temperature converter
Enter a temperature, choose its original scale, select the scale you want to convert to, and click Calculate temperature. The result panel includes the converted value, useful reference temperatures, a comparison chart, and a table for quick checking.
You can also swap the source and target scales or choose a quick example. If you change the inputs, calculate again to refresh the displayed result. For other measurement conversions, visit our converters collection, including the length conversion tool and weight conversion tool.
Understanding the main temperature scales
Celsius
Celsius is widely used in daily life and science. At standard atmospheric pressure, water freezes at 0°C and boils at 100°C.
Fahrenheit
Fahrenheit is commonly used for weather and household temperatures in the United States. Water freezes at 32°F and boils at 212°F under standard atmospheric pressure.
Kelvin
Kelvin is an absolute thermodynamic temperature scale used in science. It starts at absolute zero, and its symbol is K, without a degree sign.
Rankine and Réaumur
Rankine is an absolute scale with Fahrenheit-sized increments. Réaumur is a historical scale in which water freezes at 0°Ré and boils at 80°Ré under standard atmospheric pressure.
Temperature conversion formulas
Temperature scales use different zero points and, in some cases, different degree sizes. That is why converting a reading often requires both multiplication and addition or subtraction.
°F = (°C × 9/5) + 32°C = (°F − 32) × 5/9K = °C + 273.15°C = K − 273.15°R = (°C + 273.15) × 9/5°Ré = °C × 4/5For conversions between scales that do not have a direct formula listed here, the calculator first converts the input to Celsius and then converts that intermediate value to the target scale. This consistent method makes it easier to support multiple scales.
Worked examples
These examples show how the formulas work for common temperatures. Results are rounded for readability; use the calculator's precision setting when you need more decimal places.
| Conversion | Calculation | Result |
|---|---|---|
| 0°C to Fahrenheit | (0 × 9/5) + 32 | 32°F |
| 25°C to Fahrenheit | (25 × 9/5) + 32 | 77°F |
| 68°F to Celsius | (68 − 32) × 5/9 | 20°C |
| 0°C to Kelvin | 0 + 273.15 | 273.15 K |
| 100°C to Fahrenheit | (100 × 9/5) + 32 | 212°F |
| 20°C to Réaumur | 20 × 4/5 | 16°Ré |
Quick temperature reference table
Use this table as a starting point when comparing weather, cooking, laboratory, and everyday temperatures. Water's freezing and boiling points assume standard atmospheric pressure; those points can change with pressure.
| Reference point | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | −273.15°C | −459.67°F | 0 K |
| Water freezes | 0°C | 32°F | 273.15 K |
| Cool indoor temperature | 18°C | 64.4°F | 291.15 K |
| Room temperature example | 22°C | 71.6°F | 295.15 K |
| Warm day example | 30°C | 86°F | 303.15 K |
| Water boils | 100°C | 212°F | 373.15 K |
Temperature readings versus temperature changes
A temperature reading tells you the position on a scale. A temperature change describes the difference between two readings. The difference matters because Celsius and Fahrenheit have different-sized degrees.
A change of 1°C equals a change of 1.8°F. However, an absolute reading of 1°C is not the same as 1.8°F: 1°C equals 33.8°F. Kelvin and Celsius have equal-sized increments, so a change of 1 K is the same size as a change of 1°C.
Where temperature conversion is useful
- Weather: Compare forecasts and climate data published in different countries.
- Cooking: Convert oven temperatures between Celsius and Fahrenheit.
- Science: Use Kelvin for many thermodynamic equations and scientific measurements.
- Engineering: Keep units consistent when reading specifications or equipment documentation.
- Travel and daily life: Interpret local weather, household thermostats, and product instructions.
When working with other quantities, you may also find the volume conversion, speed conversion, and area conversion useful, if those calculator routes are available on your site.
Common temperature conversion mistakes
- Forgetting the offset: Celsius and Fahrenheit conversion requires adding or subtracting 32.
- Using the wrong order: For Fahrenheit to Celsius, subtract 32 before multiplying by 5/9.
- Adding a degree symbol to Kelvin: Write 300 K, not 300°K.
- Ignoring absolute zero: Kelvin and Rankine readings cannot be negative.
- Rounding too early: Keep full precision during calculations and round only the displayed result.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius reading by 9/5 (or 1.8), then add 32. For example, 20°C equals 68°F.
How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit reading, then multiply by 5/9. For example, 68°F equals 20°C.
What is 0°C in Fahrenheit and Kelvin?
At the freezing point of water under standard atmospheric pressure, 0°C equals 32°F and 273.15 K.
Why is Kelvin written without a degree symbol?
Kelvin is the SI unit of thermodynamic temperature. Its symbol is K, so the correct notation is 300 K.
Can Kelvin or Rankine be negative?
In ordinary thermodynamic temperature measurements, Kelvin and Rankine cannot fall below zero because both scales begin at absolute zero.
What is the difference between Rankine and Fahrenheit?
Both use the same size degree, but Rankine begins at absolute zero. Fahrenheit's zero point is different.
How many decimal places should I use?
Two decimal places are suitable for many everyday conversions. Use more precision for scientific work when the measurement accuracy justifies it.
Does water always boil at 100°C?
No. Water boils at about 100°C at standard atmospheric pressure. Its boiling point changes with pressure and altitude.