Swimming Pool Water Volume Calculator
Find out how many gallons your pool holds and what it costs to fill it based on shape and dimensions. Ideal for budgeting a new fill, partial refill, or comparing pool sizes.
About this calculator
Pool volume depends on shape. For a rectangular pool the formula is: Volume (gallons) = length × width × depth × 7.48, where 7.48 converts cubic feet to gallons. For a circular pool: Volume = π × (diameter / 2)² × depth × 7.48. For an oval pool: Volume = π × (length / 2) × (width / 2) × depth × 7.48. All three formulas first compute cubic feet of water, then multiply by 7.48052 gallons per cubic foot — the standard conversion factor. Average depth is used for pools with a gradual slope from shallow to deep end. Once volume is known, fill cost = (volume / 1000) × waterCost, giving a direct dollar figure for a complete fill at your local water utility rate.
How to use
Example: rectangular pool, 20 ft long × 10 ft wide × 5 ft average depth, water costs $4 per 1,000 gallons. Step 1 — Cubic feet: 20 × 10 × 5 = 1,000 cu ft. Step 2 — Gallons: 1,000 × 7.48 = 7,480 gallons. Step 3 — Fill cost: (7,480 / 1,000) × $4 = $29.92. For a circular pool 18 ft in diameter and 4 ft deep: Volume = 3.14159 × (9)² × 4 × 7.48 = 3.14159 × 81 × 4 × 7.48 ≈ 7,601 gallons.
Frequently asked questions
How many gallons of water does a typical backyard swimming pool hold?
An average residential rectangular pool measuring 12 × 24 ft with a 5 ft average depth holds roughly 10,800 gallons. Larger pools in the 16 × 32 ft range hold about 19,200 gallons at the same depth. Above-ground round pools are typically smaller, commonly holding 5,000–15,000 gallons. Knowing your exact volume is important for correctly dosing chemicals and estimating utility costs.
How long does it take to fill a swimming pool with a garden hose?
A standard garden hose delivers roughly 9 gallons per minute. At that rate a 10,000-gallon pool takes about 18.5 hours to fill. Using a 5/8-inch hose at city water pressure typically yields 8–12 gpm, so results vary. Many homeowners split the fill between a hose and a bulk water delivery truck to save time, especially for pools over 20,000 gallons.
What is the cheapest way to fill a swimming pool with water?
Municipal tap water via a garden hose is usually the cheapest option for pools under 15,000 gallons, with typical costs of $30–$80 depending on local rates. For larger pools, a water delivery tanker often costs less per gallon when you factor in that filling with a hose can take multiple days and may incur peak-rate surcharges. Some homeowners use well water, which avoids utility charges but requires checking well capacity to avoid running it dry. Always call your water utility first — many offer a one-time fill discount or meter adjustment for new pool fills.