Simple, and it inverts
The Magnus form — also called the August–Roche–Magnus equation — is a single exponential with just two fitted constants. Alduchov and Eskridge (1996) re-optimized those constants (17.625 and 243.04 °C) to minimize the error against accurate references over −40 to +60 °C, where it stays within about 0.4%. It is the recommended meteorological set.
Its defining advantage is algebraic: because the temperature appears in a simple ratio inside the exponential, the equation can be solved for temperature in closed form. That inversion is exactly the dew-point formula, using the same two constants.
Where it shines, and where it fades
Reach for Magnus in meteorology and humidity work near ambient temperatures, and whenever you need the dew-point relationship. The same constants power this site's dew point calculator, so the two stay perfectly consistent.
Above roughly 60 °C the two-constant fit drifts; for hot or high-pressure conditions switch to Buck or IAPWS-95.
Compare with other formulas
See this and every other formula side by side, with the live deviation from IAPWS-95 at your temperature, on the main calculator. The Antoine equation has its own page.
References
Every formula on this page is implemented from, and validated against, the following primary standards and papers.
- Improved Magnus Form Approximation of Saturation Vapor Pressure — Alduchov & Eskridge 1996, J. Appl. Meteorol. 35:601
- IAPWS R6-95(2018) / Wagner & Pruss 2002 — International Association for the Properties of Water and Steam — the reference standard
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