HVAC ENGINEERING TOOL

Dew Point Calculator

Calculate dew point from dry-bulb temperature and relative humidity within the documented range.

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Formula / Method

γ = ln(RH/100) + aT/(b+T); Td = bγ/(a−γ)

Engineering Method & Assumptions

Magnus approximation over liquid water; a=17.625, b=243.04 °C.
Valid only from 0–60 °C and 1–100% RH.
Not a frost-point calculation.

Applicability: Do not use this Phase 1 method for sub-zero dry-bulb conditions or frost-point determination.

WHEN TO USE THIS TOOL

Useful during psychrometrics & coils work.

Evaluate moist-air conditions, dew point, condensation risk and cooling/dehumidification processes.
Check how temperature, humidity and pressure assumptions affect the resulting air state.
Support coil, cleanroom, comfort and humidity-control discussions with traceable calculations.

Frequently asked questions

What is dew point?

Dew point is the temperature at which air reaches saturation when cooled at approximately constant pressure and moisture content.

What happens at 100% RH?

The calculated dew point equals the dry-bulb temperature within numerical tolerance.

Does this tool calculate frost point?

No. It uses an approximation over liquid water and does not calculate frost point.