Tools
Calculators
Run your own numbers instead of trusting a box label. Each calculator shows its formula and assumptions so you can check the result.
- Swamp Cooler Temperature Calculator
Enter outdoor temperature and humidity to get the wet bulb, the supply air temperature your swamp cooler can reach, and a clear verdict on whether it will work.
- Swamp Cooler Size Calculator (CFM)
Calculate the CFM your evaporative cooler needs from floor area, ceiling height and climate, with an allowance for ductwork and a recommended unit type.
- Swamp Cooler Water Usage Calculator
Estimate how many gallons per hour, day and month your evaporative cooler uses, including bleed-off, and what that water costs at your local rate.
- Swamp Cooler vs Air Conditioner Running Cost Calculator
Compare the monthly cost of running an evaporative cooler against central air conditioning, including the cooler's water, using your own electricity rate.
- DataSwamp Cooler Climate Index
Calculated cooling performance for U.S. cities on a hot design day, with aspen and rigid media.
The formulas behind the calculators
All calculators run in your browser and use standard psychrometric relationships. Wet-bulb temperature is computed from dry-bulb temperature and relative humidity with the Stull (2011) approximation, which is accurate to within about 1 °F for normal weather at sea-level pressure. Supply air temperature uses the saturation efficiency equation:
Water use comes from the energy balance: every degree of sensible cooling on 1 CFM is 1.08 BTU/h, and every pound of water evaporated absorbs about 1,060 BTU. That reduces to gallons per hour = CFM × temperature drop ÷ 8,186. Read the editorial standards for how we choose defaults.