Psychrometric Calculator
Dew point, humidity ratio, enthalpy, wet-bulb and vapour pressure from dry-bulb & RH.
The whole psych chart in one card. 25 °C/50% RH = 9.9 g/kg, 50.3 kJ/kg, dew point 13.9 °C — memorize that anchor point and you can sanity-check anything.
Formula
Psychrometric Calculator is a free psychrometric calculator for HVAC designers, technicians and energy auditors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Psychrometric Calculator
Dew point, humidity ratio, enthalpy, wet-bulb and vapour pressure from dry-bulb & RH. The calculation implements p_v = RH·p_sat(T); w = 0.622·p_v/(p−p_v); h = 1.006T + w(2501+1.86T) (ASHRAE Handbook — Fundamentals, ch. 1 (psychrometrics); Stull (2011) wet-bulb approximation). The whole psych chart in one card. 25 °C/50% RH = 9.9 g/kg, 50.3 kJ/kg, dew point 13.9 °C — memorize that anchor point and you can sanity-check anything.
How to use Psychrometric Calculator
- 1Enter Dry-bulb temperature in °C.
- 2Enter Relative humidity in %.
- 3Enter Barometric pressure in kPa.
- 4Read Dew point, Humidity ratio, Enthalpy instantly — no submit button needed.
Why use Psychrometric Calculator?
- ✓Implements the standard formula — p_v = RH·p_sat(T); w = 0.622·p_v/(p−p_v); h = 1.006T + w(2501+1.86T)
- ✓Reference cited on-page: ASHRAE Handbook — Fundamentals, ch. 1 (psychrometrics); Stull (2011) wet-bulb approximation
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Psychrometric Calculator use?+
It computes p_v = RH·p_sat(T); w = 0.622·p_v/(p−p_v); h = 1.006T + w(2501+1.86T), per ASHRAE Handbook — Fundamentals, ch. 1 (psychrometrics); Stull (2011) wet-bulb approximation. The formula is displayed under the result.
What should I keep in mind when using this calculator?+
The whole psych chart in one card. 25 °C/50% RH = 9.9 g/kg, 50.3 kJ/kg, dew point 13.9 °C — memorize that anchor point and you can sanity-check anything.
Is this based on ASHRAE methods?+
The calculations follow the standard ASHRAE/ISHRAE formulations cited under the result, simplified where industry practice does the same. For permit-grade design, confirm with the full code procedure.
Is the Psychrometric Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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