Temperature converter
All three scales at once. Type in any one field and the other two follow.
All three scales at once. Type in any one field and the other two follow.
Three scales, two offsets and one ratio. Celsius and Kelvin share a step size and differ only by a fixed offset; Fahrenheit has a step that is five ninths as large and a zero of its own.
Worked example. "Try an example" loads 37 °C, the temperature of a mammalian cell incubator. Fahrenheit: 37 × 9/5 = 66.6, plus 32 gives 98.6 °F. Kelvin: 37 + 273.15 gives310.15 K. Type 98.6 into the Fahrenheit field instead and the other two fields return to 37 and 310.15, because the conversion is exact in both directions.
These are the settings a protocol actually asks for, from cryogenic storage to the autoclave.
| °C | °F | K | Where it is used |
|---|---|---|---|
| −196 | −320.8 | 77.15 | Liquid nitrogen, cryogenic storage |
| −80 | −112 | 193.15 | Ultra-low freezer: cells, competent cells, enzymes in glycerol |
| −20 | −4 | 253.15 | Standard freezer: primers, dNTPs, enzymes |
| 0 | 32 | 273.15 | Ice bath, wet ice |
| 4 | 39.2 | 277.15 | Fridge and cold room: plates, antibodies, gels |
| 25 | 77 | 298.15 | Room temperature, the standard state of most constants |
| 30 | 86 | 303.15 | Yeast and slow bacterial growth |
| 37 | 98.6 | 310.15 | Mammalian incubator, E. coli growth, body temperature |
| 42 | 107.6 | 315.15 | Heat shock of chemically competent cells |
| 56 | 132.8 | 329.15 | Heat inactivation of serum, proteinase K digestion |
| 65 | 149 | 338.15 | Heat inactivation of many restriction enzymes |
| 72 | 161.6 | 345.15 | Taq extension step |
| 95 | 203 | 368.15 | PCR denaturation step |
| 100 | 212 | 373.15 | Boiling water bath |
| 121 | 249.8 | 394.15 | Autoclave, 15 minutes at 15 psi above atmospheric |
The gap between a −20 °C freezer and a −80 °C freezer is the one worth remembering in Fahrenheit, because they are sold as −4 °F and −112 °F units. A frost-free household freezer cycles above −20 °C to defrost itself and is not a substitute for either.
Kelvin starts at absolute zero, so it is the scale that appears in physical equations: the gas constant term RT in binding and reaction thermodynamics, nearest-neighbour melting temperature models, and the Arrhenius equation for reaction rates. A ΔG value quoted at 25 °C is calculated at 298.15 K, which the ΔG to Kd converter uses as its default. Never write "degrees Kelvin" or K with a degree sign: the unit is the kelvin, symbol K.
95 °C separates the strands, an annealing step near 55 to 65 °C lets the primers bind, and 72 °C is close to the optimum of Taq polymerase, which is why extension is run there. Annealing is the step that needs thought rather than conversion, since it follows the melting temperature of the primers; the PCR troubleshooting guide covers how to choose it and the melting curve tool shows how a duplex comes apart as the temperature rises.
Multiply by 9, divide by 5 and add 32: °F = °C × 9/5 + 32. A 37 °C incubator is 37 × 1.8 + 32 = 98.6 °F. Going the other way, subtract 32 first: °C = (°F − 32) × 5/9.
Add 273.15: K = °C + 273.15. The two scales have the same step size, so a difference of 10 °C is a difference of 10 K. Kelvin is written without a degree sign and never as "degrees Kelvin".
At −40. The two scales cross there, which is why −40 °C and −40 °F are the same temperature. Absolute zero is 0 K, −273.15 °C or −459.67 °F, and nothing can be colder.
Because that is the temperature of saturated steam at about 15 psi above atmospheric pressure, and 15 minutes of it kills bacterial spores. In Fahrenheit that is 249.8 °F, which is why older American autoclaves are marked 250 °F.
The fields carry the exact conversion, the headline rounds to two decimals. Celsius to Fahrenheit adds one decimal place in most cases (4 °C is 39.2 °F), and Kelvin keeps the .15 that comes from the offset unless the Celsius value ends in .85.