Pool Volume Calculator
Calculate swimming pool volume in gallons and liters for chemical treatment, filling, and heating estimates.
Your Pool Volume
- Measure length and width — for rectangular pools. For oval pools, use the longest and widest points.
- Calculate average depth — add the shallow end depth and deep end depth, then divide by 2.
- Select your pool shape — rectangular pools multiply length × width × depth. Round and oval pools use a 0.785 shape factor.
- Use gallons for chemicals — all pool chemical dosing instructions are based on pool volume in gallons or liters.
- Estimate fill time — a standard ¾-inch garden hose delivers about 9–17 GPM depending on water pressure.
Why Pool Volume Matters
Knowing your pool's volume in gallons is essential for every aspect of pool ownership. Chemical dosing — chlorine, pH adjusters, algaecide, shock — is always calculated per 10,000 gallons. Getting this wrong means either an undertreated pool (algae, bacteria) or an overtreated one (skin and eye irritation, bleached liners).
Pool volume is also used to size your pump and filter system correctly. The industry standard is to turn over the entire pool volume every 8 hours. A 20,000-gallon pool needs a pump capable of at least 2,500 gallons per hour (42 GPM) to meet this standard. Heater sizing and heating cost estimates also depend directly on accurate volume.
Pool Volume by Shape
Use the correct formula for your pool shape:
| Pool Shape | Formula | Shape Factor |
|---|---|---|
| Rectangular | Length × Width × Avg Depth × 7.48 | 1.0 |
| Round / circular | Diameter² × Avg Depth × 5.87 | 0.785 |
| Oval | Length × Width × Avg Depth × 5.87 | 0.785 |
| Kidney / freeform | Length × Width × Avg Depth × 7.48 × 0.85 | ~0.85 |
| L-shaped | Split into two rectangles, sum volumes | 1.0 each |
The 7.48 factor converts cubic feet to US gallons. The 0.785 factor accounts for the circular cross-section of round and oval pools. For irregular shapes, break the pool into simpler sections and add the volumes together.
Common Pool Sizes — Volume Reference
| Pool Size | Avg Depth | Gallons (US) | Liters |
|---|---|---|---|
| 12 × 24 ft (rectangular) | 4.5 ft | 9,694 | 36,700 |
| 16 × 32 ft (rectangular) | 5 ft | 19,200 | 72,700 |
| 18 × 36 ft (rectangular) | 5.5 ft | 26,730 | 101,200 |
| 20 × 40 ft (rectangular) | 5.5 ft | 33,000 | 124,900 |
| 15 ft round | 4 ft | 5,298 | 20,060 |
| 24 ft round | 4.5 ft | 15,268 | 57,800 |
Average depth = (Shallow end + Deep end) ÷ 2. Values are approximate and assume flat-bottom pools.
Pool Volume Formulas
Volume calculations by shape:
Round (gallons) = Diameter (ft)² × Avg Depth (ft) × 5.87
Oval (gallons) = Length (ft) × Width (ft) × Avg Depth (ft) × 5.87
Gallons to liters = Gallons × 3.785
Pump turnover rate = Pool Volume (gal) ÷ 8 hours ÷ 60 = GPM needed
For pools with a sloped bottom, calculate average depth as (shallow depth + deep depth) ÷ 2. For a true hopper-bottom pool, the calculation is more complex and should be done in sections.
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Frequently Asked Questions
How do I find the average depth of my pool?
For a pool with a sloped bottom, average depth = (shallow end depth + deep end depth) ÷ 2. For example, a pool that is 3 feet at the shallow end and 6 feet at the deep end has an average depth of 4.5 feet. For pools with a flat bottom throughout, the average depth is simply the actual depth.
How many gallons of water does a typical swimming pool hold?
A standard residential pool (16 × 32 ft, 5 ft average depth) holds approximately 19,200 gallons. Small above-ground pools can be as little as 5,000 gallons, while large in-ground pools can exceed 30,000 gallons. Above-ground round pools typically range from 5,000 to 15,000 gallons.
How long does it take to fill a pool with a garden hose?
A standard ¾-inch garden hose delivers 9–17 gallons per minute (GPM) depending on your water pressure. At 10 GPM, a 20,000-gallon pool takes about 33 hours (roughly 2 days) to fill. Running the hose continuously overnight is the most common approach. Check your local water utility — some offer a one-time pool fill allowance at a reduced rate.
How much chlorine do I need based on pool volume?
As a starting point, a new pool or a pool being shocked needs about 1 pound of granular chlorine (calcium hypochlorite) per 10,000 gallons to raise the chlorine level by approximately 5 ppm. For routine maintenance, dosing rates vary by product — always follow the label instructions, which are based on pool volume in gallons.
How do I convert gallons to liters?
1 US gallon is about 3.785 liters. If you have cubic meters (m³), multiply by 1,000 to get liters. This calculator can show both gallons and liters so you can match product labels and dosing instructions.