K = °C + 273.15
Temperature scales require both a scale and an offset.Conversion lab / temperature
Celsius to Kelvin Converter
Convert degrees Celsius to kelvins using the exact 273.15 offset.
Celsius to Kelvin Converter: Turn a Celsius measurement into an absolute temperature for a science worksheet or an equation requiring kelvin. The two scales have equal-sized steps but different origins. Enter a reading in °C, then use the resulting K value wherever the calculation specifies absolute temperature. Runs 100% locally in your browser with zero server file uploads.
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Result / live
274.15
Kkelvins
-273.15 °C0 K
-40 °C233.15 K
0 °C273.15 K
20 °C293.15 K
100 °C373.15 K
Degrees Celsius to kelvins conversion table
| degrees Celsius (°C) | kelvins (K) |
|---|---|
| -273.15 °C | 0 K |
| -260 °C | 13.15 K |
| -240 °C | 33.15 K |
| -220 °C | 53.15 K |
| -200 °C | 73.15 K |
| -180 °C | 93.15 K |
| -160 °C | 113.15 K |
| -140 °C | 133.15 K |
| -120 °C | 153.15 K |
| -100 °C | 173.15 K |
| degrees Celsius (°C) | kelvins (K) |
|---|---|
| -80 °C | 193.15 K |
| -60 °C | 213.15 K |
| -40 °C | 233.15 K |
| -20 °C | 253.15 K |
| 0 °C | 273.15 K |
| 20 °C | 293.15 K |
| 40 °C | 313.15 K |
| 60 °C | 333.15 K |
| 80 °C | 353.15 K |
| 100 °C | 373.15 K |
Rounded to seven significant digits; the converter above uses the full factor.
Adding the absolute-zero offset
Let C represent a Celsius temperature and T its kelvin value. T = C + 273.15. For C = 25, the full calculation is 25 + 273.15 = 298.15 K. For C = −273.15 the result is 0 K. Multiplication by a fixed factor alone would always map zero to zero, which is why this conversion is affine rather than proportional.
NIST (https://www.nist.gov/pml/owm/si-units-temperature) confirms that one Celsius degree is an interval of one kelvin. Adding the exact offset does not supply measurement precision that the original sensor lacks.
Ratios need an absolute origin
A comparison such as twice the absolute temperature uses kelvin values, not twice the Celsius number. For instance, 20 °C and 40 °C are not in a two-to-one absolute-temperature ratio. The familiar crossover −40 °C = −40 °F occurs because x = 9x/5 + 32 gives x = −40; both readings correspond to 233.15 K.
How to use it
- Enter the temperature in degrees Celsius.
- Read the converted kelvins value as it updates.
- Use the common values or open the reverse conversion to cross-check.
Privacy & limitations
Your value never leaves this browser. JavaScript floating-point arithmetic can round the last displayed digit; this general utility is not a substitute for calibrated or regulated measurement systems.
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Frequently asked questions
Why must I add 273.15 before using a gas-law temperature?
An equation that uses absolute temperature expects the distance from absolute zero. A reading of 25 °C is 298.15 K. Substituting 25 into a formula that expects kelvin changes the physical quantity, even though Celsius and kelvin intervals have equal size.
Is the output written °K or K?
Use K, without a degree sign: 298.15 K. The unit name is kelvin in lower case, and the symbol is a capital K. Celsius keeps its degree sign, as in 25 °C.
Do I add 273.15 to a Celsius difference too?
No. A difference of 10 °C is a difference of 10 K. Only an actual reading receives the offset: 10 °C as a temperature is 283.15 K. A 10 °C difference also equals 18 °F because Fahrenheit intervals have another size.
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