Pool Evaporation Calculator

Estimate annual water loss from pool evaporation based on pool surface area, climate, and whether a cover is used.

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sq ft
inches/month
months
%

Annual Water Loss

6,728 gallons

Monthly Water Loss1,121 gallons
Annual Refill Cost34 USD
Cover Would Save4,710 gallons

Annual Water Loss vs Pool Season Months

View formula & how it works →

How to Calculate Pool Evaporation

Swimming pools lose significant water to evaporation, especially in hot, dry, or windy climates.

Formula

Evaporation (gal) = Pool Area * Evap Rate * Months * 0.623 * (1 - Cover Reduction)

Typical Evaporation Rates

  • Humid climate: 2-3 inches/month
  • Moderate: 4-5 inches/month
  • Arid/hot: 6-8 inches/month

    • A pool cover reduces evaporation by 70-90%.

    Example Calculation

    A 450 sq ft pool evaporating 4 inches/month for 6 months without a cover.

    1. 01Gross evaporation: 450 * 4 * 6 * 0.623 = 6,729 gallons
    2. 02Net evaporation (no cover): 6,729 gallons
    3. 03Monthly loss: 6,729 / 6 = 1,122 gallons
    4. 04Cover would save: 6,729 * 70% = 4,710 gallons

    Frequently Asked Questions

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