Dew Point Calculator
Surfaces below the dew point collect condensation.
HVAC Pro calculator — inputs, formula and example are open to everyone.
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Formula
- γ = ln(RH/100) + a·T/(b + T)
- Td = b·γ ÷ (a − γ) (a = 17.62, b = 243.12 °C)
Example calculation
75 °F at 50% RH → dew point ≈ 55 °F.
Practical HVAC use
Duct sweating, window condensation and coil performance.
Common mistakes
- Measuring RH near a humidity source.
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Educational tool. Results are estimates from the stated formulas; always confirm with manufacturer data and the code adopted in your jurisdiction. All calculators