Enter a stable air reading, then compare the estimate with the surface you are investigating.
Estimated dew point
A surface at or below this temperature may collect condensation.
Magnus approximation. Sensor accuracy, local airflow and surface measurement affect the comparison.
Formula and limits
The calculator converts to Celsius and uses the Magnus approximation: γ = ln(RH/100) + aT/(b+T), then Td = bγ/(a−γ), with a = 17.62 and b = 243.12°C. It is intended for ordinary indoor screening—not engineering design or material diagnosis.
How to use the answer
Compare the estimate with a safe surface-temperature reading. A surface below dew point supports a condensation explanation, but it does not exclude a leak. Use timing, location and weather observations too.
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