Estimate gallons lost to evaporation and the resulting refill cost.
This calculator estimates how much water a pool loses from evaporation based on surface area and the number of inches lost each week. It then converts that water loss into gallons and estimates the cost of replacing it through an auto-fill system or manual refill.
Because evaporation happens across the water surface, surface area matters more than total pool gallons for this calculation.
Water loss increases with heat, wind, low humidity, warm pool water, waterfalls, deck jets, spas, and other features that expose more water to air. Covers and windbreaks can reduce evaporation significantly.
Some weekly water loss is normal, but unusually high loss may point to a leak, overflow problem, or auto-fill malfunction.
An auto-fill keeps the water level steady, which is convenient, but it can also hide a slow leak. The pool may look normal while the utility bill climbs. Tracking refill volume or comparing water use over time can expose the problem.
Mark the water level or use a bucket test over a known time period. Compare the pool’s drop with water inside a partially submerged bucket.
Normal loss varies widely by climate, wind, humidity, water temperature, and cover use. Track your own pool under typical conditions instead of relying on one universal number.
Yes. A cover reduces evaporation and can lower both water cost and heating cost.
If the pool loses more water than a bucket test under the same weather conditions, a leak becomes more likely and should be investigated.
An auto-fill can make a leaking pool look perfectly normal. Watch the meter, the bill, or the refill volume—not just the waterline.