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Rule-of-thumb estimator. Real evaporation varies with sun, wind, humidity, cover use, water temperature, and pool location.
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Evaporation Estimator Guide
How the Calculator Works
This calculator estimates daily evaporation using air temperature, water temperature, humidity, wind speed, pool surface area, and cover usage. The result is a practical estimate, not an exact measurement.
Why It Matters
- Estimate normal water loss.
- Spot possible leaks when water loss is excessive.
- Plan makeup water usage.
- Reduce chemical dilution.
Recommended Ranges
- Many pools lose about 1/8 to 1/4 inch per day during warm weather.
- Hot, windy, dry conditions can produce significantly higher evaporation.
- A quality cover can greatly reduce water loss.
Common Mistakes
- Assuming every drop in water level is evaporation.
- Ignoring splash-out and backwashing.
- Not considering wind and humidity.
- Forgetting that leaks can mimic evaporation.
Frequently Asked Questions
How much evaporation is normal?
Most outdoor pools lose roughly 1–2 inches per week depending on the weather.
Can a cover help?
Yes. Covers dramatically reduce evaporation and help retain heat.
How do I know if I have a leak?
If water loss consistently exceeds expected evaporation, perform a bucket test.
Pool Gal Pro Tip 💦
If you're adding water every few days, compare your estimated evaporation to your actual water loss. If the numbers don't match, investigate for leaks before adding more chemicals.
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