Calculator
Unit conversion
Equivalent quantities with the calculation shown below.
Equivalent values
| Unit | Value |
|---|---|
| Celsius (°C) | 25 |
| Fahrenheit (°F) | 77 |
| Kelvin (K) | 298.15 |
A temperature value needs an offset
Celsius and Fahrenheit differ in both scale interval and zero point. For a temperature value, use °F = °C × 1.8 + 32. Reverse it by subtracting 32 before dividing by 1.8. Kelvin uses K = °C + 273.15. Thus 0 °C, 32 °F and 273.15 K indicate the same temperature. The tool rejects absolute temperature values below absolute zero.
Do not add 32 to a temperature difference
For chilled water supplied at 7 °C and returning at 12 °C, the difference is 5 °C or 5 K. In Fahrenheit intervals that is 5 × 1.8 = 9 °F. Converting the readings separately gives 44.6 °F and 53.6 °F; subtracting them still gives 9 °F. Select “Temperature difference (ΔT)” to omit zero-point offsets. Reporting this interval as 41 °F incorrectly applies the temperature offset.
Record units, timestamps and subtraction order
Compare supply and return readings from the same circuit at the same time. Converting °C to K cannot correct a calibration error. This tool expresses one value in another unit; it does not choose the subtraction order for two readings. Return minus supply and supply minus return have opposite signs. State both the unit and subtraction order in the control description or report.
Worked examples
Room temperature
25 °C × 1.8 + 32 = 77 °F. Reverse conversion: (77 − 32) / 1.8 = 25 °C.
Chilled-water difference
12 − 7 = 5 °C difference = 5 K difference = 9 °F difference. Use difference mode for this calculation.
Cold operating range
−40 °C × 1.8 + 32 = −40 °F. The same temperature is 233.15 K.
Definitions and calculation method
Unit factors and temperature-scale relationships: NIST SP 811, Appendix B.8 ↗.
Application examples were prepared for this page. Values are converted through the reference unit before display rounding; displayed results use up to 12 significant digits. A converted reading retains the uncertainty of the original measurement.