Updated October 2026
Searches for a "Carrier psychrometric chart" usually mean one of two things: the historical chart produced by Carrier Corporation, or the modern digital psychrometric tools the company still publishes. Both trace back to the same foundational figure in the field.
Willis Carrier — inventor of modern mechanical air conditioning and founder of what became Carrier Corporation — presented a paper titled "Rational Psychrometric Formulae" to the American Society of Mechanical Engineers in 1911. That paper laid out, for the first time in a systematic engineering form, the relationships between dry-bulb temperature, wet-bulb temperature, humidity, dew point and enthalpy that still underpin every psychrometric chart and calculator in use today — including the Tetens-based formulas this site runs. It's one of the genuinely foundational documents in HVAC engineering, not just a historical footnote.
Carrier Corporation has long published its own psychrometric chart, widely distributed in HVAC training materials and still a recognizable reference alongside ASHRAE's version. Functionally, it plots the same physical quantities — dry-bulb, wet-bulb, humidity ratio, RH, enthalpy, specific volume — using the same underlying thermodynamics; the differences from an ASHRAE chart are mainly presentation and branding rather than a different physical model. Carrier also publishes E20-II, a long-standing digital psychrometric analysis program used throughout the industry as the software equivalent of the printed chart, for engineers who need to chain multiple process points together.
Because all of these tools — ASHRAE's chart, Carrier's chart, Carrier's E20-II software, and this calculator — ultimately implement the same family of psychrometric relationships Willis Carrier first formalized in 1911, a given dry-bulb/RH input should produce matching results (within each tool's own formula precision and rounding) regardless of which one you use. The thermodynamics doesn't change based on whose name is printed on the chart; what differs between tools is mainly interface, precision, and whether barometric pressure is a fixed chart assumption or, as here, a direct input you control yourself (see the altitude page).
If your training or workplace uses Carrier-branded materials specifically, there's no need to mentally "convert" anything when switching to this calculator (or to an ASHRAE chart) — the numbers you get for RH, wet-bulb, dew point and enthalpy should match within normal precision, because they're reading off the same physical relationships Carrier's own 1911 work established.