Evaporative cooler calculator
A swamp cooler chills air by evaporating water into it — so it works brilliantly in dry heat and barely at all when it's humid. Enter the conditions to estimate the cooled air temperature.
Evidence-checked. Facts and figures on this page are verified against published standards and government sources (Wet-bulb temperature (Stull approximation) at ~85% cooler efficiency). Last verified July 2026 — our methodology.
Estimated cooled air
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- Temperature drop
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- Wet-bulb (the floor)
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- How well it works
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Evaporation can only cool air down toward its wet-bulb temperature — the theoretical limit — and a real cooler reaches roughly 80–90% of the way there (this uses 85%). Dry air has a wet-bulb far below the actual temperature, so the drop is large; humid air has a wet-bulb close to the temperature, so there's almost nothing to gain. A swamp cooler also adds moisture to the room, which is the opposite of what you want in a humid climate.
When a swamp cooler is worth it
In the dry Southwest, an evaporative cooler can drop the air 15–30°F for a fraction of an air conditioner's energy. In a humid climate it barely cools and makes the mugginess worse — a heat pump or AC (whichremoves moisture) is the better call there. A rough rule: swamp coolers shine when the humidity is low, which you can gauge with thedew point calculator or the 7-day mugginess forecast. If dryness is your problem instead, seeliving with desert low humidity.