Your result
What your result means
0 °C is 0 °C °C, 32 °F °F and 273.15 K K, using the exact conversions. Figures on screen are rounded half-up to 0.01 degree. This is a change of scale, not a weather or cooking estimate.
The math
Formula and sources
°F = (°C × 1.8) + 32 K = °C + 273.15 °C = (°F − 32) / 1.8 °C = K − 273.15
- 1.8
- exactly 9/5. One Celsius degree is 1.8 Fahrenheit degrees.
- 273.15
- exact offset. 0 °C is 273.15 K. Absolute zero is 0 K.
NIST’s “Touchstone temperatures” table rounds kelvin to the nearest degree (0 °C is listed as 273 K) and labels that table approximate. This converter follows NIST’s exact conversion table instead, so 0 °C is 273.15 K and 100 °C is 212 °F and 373.15 K. Water’s boiling point depends on pressure; NIST says water boils at about 100 °C, so 100 °C here is only the scale conversion.
The code and tests for this formula are open source (MIT): temperature.ts on GitHub.
Sources we checked this against
- 1SI Units – Temperature (exact conversion table; 0 °C = 273.15 K)National Institute of Standards and Technology · nist.gov
Formula last checked 2026-11-06. Found an error? Tell us and we will fix it.
Step by step
Two worked examples
Ice point
Fahrenheit
32 °F
- Temperature
- 0
- Scale
- °C
0 °C × 1.8 + 32 = 32 °F °F. 0 + 273.15 = 273.15 K K. NIST states that zero degrees Celsius is 273.15 kelvin.
The point where the scales meet
Fahrenheit
-40 °F
- Temperature
- -40
- Scale
- °C
−40 × 1.8 + 32 = -40 °F. Celsius and Fahrenheit are the same number at −40. Kelvin is −40 + 273.15 = 233.15 K.
| Result | Example 1 | Example 2 |
|---|---|---|
| Fahrenheit | 32 °F | -40 °F |
| Kelvin | 273.15 K | 233.15 K |
Questions
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 1.8 and add 32. 0 °C is 32 °F. 100 °C is 212 °F. The 1.8 is exactly 9/5, from NIST’s exact conversion table.
How do I convert Celsius to kelvin?
Add 273.15. NIST states that zero degrees Celsius is 273.15 kelvin, and that one Celsius degree is an interval of 1 kelvin. A chart that says 0 °C is 273 K has rounded to the nearest kelvin.
Is 100 °C the boiling point of water?
NIST says water boils at about 100 °C, because the boiling point moves with air pressure. The converter still turns 100 °C into exactly 212 °F and 373.15 K. That is the scale, not a claim about your kitchen.
What is absolute zero?
0 K. On the Celsius scale that is −273.15 °C, and on the Fahrenheit scale it is −459.67 °F. The converter will not go below that.