How to Calculate Dew Point
What is Dew Point?
The dew point is the temperature to which air must be cooled for water vapour to condense. Unlike relative humidity, dew point is an absolute moisture measure that stays constant when temperature changes.
Formula
Step-by-Step Guide
- 1Uses the Magnus formula: alpha = ln(RH/100) + (a × T)/(b + T)
- 2Constants: a = 17.625, b = 243.04 degrees C
- 3Dew Point = (b × alpha) / (a − alpha)
- 4Dew point above 21°C feels humid; above 24°C feels oppressive
Worked Examples
Frequently Asked Questions
What is Dew Point?
The dew point is the temperature to which air must be cooled for water vapour to condense. Unlike relative humidity, dew point is an absolute moisture measure that stays constant when temperature changes
How accurate is the Dew Point calculator?
The calculator uses the standard published formula for dew point. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.
What units does the Dew Point calculator use?
This calculator works with inches, Celsius. You can enter values in the units shown — the calculator handles all conversions internally.
What formula does the Dew Point calculator use?
The core formula is: Uses the Magnus formula: alpha = ln(RH/100) + (a × T)/(b + T). Each step in the calculation is shown so you can verify the result manually.
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