Humidity after heating calculator
Estimate how relative humidity changes when air is heated without adding or removing water vapour.
Heating lowers relative humidity without removing water vapour under this assumption. It does not fix a leak or remove moisture from materials.
Enter your measurements, then calculate.
Method and limitations
Uses the same Magnus saturation pressure over liquid water as the dew point tool, with a = 17.625, b = 243.04 °C and 6.1094 hPa. T1 and T2 are in °C; RH1 and RH2 are percentages. Both temperatures must be within −40 to 50 °C and T2 ≥ T1. Vapour pressure stays constant. Ventilation, moisture sources, dehumidification and changes in total pressure are excluded. eₛ(T) = 6.1094 × exp(a × T / (b + T)) hPa; RH2 = RH1 × eₛ(T1) / eₛ(T2).
Sources
- Improved Magnus Form Approximation of Saturation Vapor Pressure, equation 21 — O. A. Alduchov & R. E. Eskridge — American Meteorological Society (1996), copy hosted by NAU,
- Handbook 44 (2023), Appendix C — Units of measurement — NIST,