How to Calculate Dew Point Temperature
What is Dew Point Temperature?
Dew Point Temperature Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.
Formula
Td ≈ T - ((100 - RH) / 5) (Magnus approximation)
Step-by-Step Guide
- 1Enter current temperature and relative humidity
- 2Apply the formula using your project measurements
- 3Add required safety factors or waste allowances per code
Worked Examples
Input
75°F air temperature, 60% RH
Result
Dew Point ≈ 75 - (40/5) = 75 - 8 = 67°F
Common Mistakes to Avoid
- ✕Not applying code-required safety factors or derating
- ✕Forgetting to account for waste and cut losses in material estimates
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