Condensation & Dew Point Calculator
Find the dew point and condensation risk
The dew point is the temperature at which air becomes saturated and water begins to condense. Enter your indoor temperature and relative humidity to find it, and add a surface temperature to check whether a cold window or wall is at risk of condensation.
Dew point
13.2°C
Air at these conditions will form condensation on any surface at or below 13.2°C. Measure a cold surface (e.g. a window or external wall) to compare.
Calculated with the Magnus formula. Actual mould growth depends on sustained conditions and other factors, not a single reading.
How to read the results
If a surface is at or below the dew point, condensation will tend to form on it. Raising the surface temperature (insulation, heating), lowering indoor humidity or improving ventilation all increase the safety margin. A single reading does not prove a mould problem — sustained conditions matter more.
Frequently asked questions
The Magnus-Tetens approximation, a widely documented method. It is an approximation suitable for everyday indoor conditions, not a laboratory measurement.