Pool Volume Calculator
Find your pool volume in gallons and liters for chemical dosing, filling, and heater sizing.
For a round pool, enter the diameter here too.
Leave one depth blank for a constant-depth pool; the calculator averages the two.
Your Pool Volume
- Select pool shape - shape sets the multiplier - round and oval pools hold about 78.5% of their bounding box.
- Enter length and width - use the longest and widest points; for a round pool, enter the diameter in both fields.
- Enter both depths - the calculator averages shallow and deep ends automatically.
- Dose chemicals by gallons - all chlorine, pH, and shock instructions are written per gallon (usually per 10,000).
- Check the fill estimate - based on a typical garden hose at about 12 gallons per minute.
A 16 by 32 foot rectangular pool averaging 5.5 feet deep holds about 21,000 gallons - the number every chemical dose, pump, and heater size keys off. Average depth is just the shallow and deep readings averaged, so a 3 foot shallow end and an 8 foot deep end give 5.5. Round and oval pools hold about 21.5 percent less than the rectangle around them, and kidney shapes about 15 percent less. Enter your shape and depths above.
Average Depth Drives the Gallons
Why Pool Volume Matters
Your pool's volume in gallons drives every part of ownership. Chemical dosing - chlorine, pH adjusters, algaecide, shock - is always written per a set number of gallons, usually per 10,000. Guess the volume and you either under-treat (algae and cloudy water) or over-treat (irritated skin and eyes, bleached liners).
Volume also sizes your equipment. The industry standard is to turn the whole pool over every 8 hours, so a 20,000-gallon pool needs a pump moving at least about 42 gallons per minute. Heater sizing and heating-cost estimates depend on volume too. Get the gallons right once and every downstream decision gets easier.
Pool Volume by Shape
Each shape uses a different multiplier on its bounding dimensions:
| Pool Shape | Volume Formula | Shape Factor |
|---|---|---|
| Rectangular | Length × Width × Avg Depth × 7.48 | 1.00 |
| 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 |
Pool Volume Formulas
The conversions used:
Cubic feet = Length × Width × Avg depth × Shape factor
US gallons = Cubic feet × 7.48
Liters = US gallons × 3.785
Water weight = US gallons × 8.34 lb
Fill time assumes a standard garden hose flowing about 12 gallons per minute (720 gallons per hour); real flow varies with pressure and hose diameter.
Why Average Depth Works, and How to Dose From It
For a pool whose floor slopes evenly from the shallow end to the deep end, the average depth is simply the two end depths averaged - the extra volume under the deep half exactly balances what is missing under the shallow half. A pool with a diving hollow, a beach entry, or an attached spa needs each section measured and added on its own, because the slope is no longer constant.
Once the gallons are set, almost every chemical is dosed as a rate per 10,000 gallons: a typical shock is about one pound per 10,000, and stabilizer, algaecide, and pH adjusters are labeled the same way. An accurate volume is what keeps you from over- or under-treating the water, which is why it is the first number to lock down before sizing a pump or heater.
Next Steps
Volume set, finish the pool area:
Related Calculators
Setting a pool deck or surround? Size the base and finish in the landscaping calculator collection.
Frequently Asked Questions
How many gallons is a 32 × 16 pool?
A 32 × 16 ft rectangular pool with an average depth of 5 ft holds about 19,150 gallons (32 × 16 × 5 × 7.48). Pools rarely have a flat bottom, so enter your real shallow and deep depths and the calculator averages them for you.
How do I calculate the volume of a round pool?
Enter the diameter in both the length and width fields and choose the Round shape. The calculator applies the 0.785 factor, which is the same as the standard diameter² × average depth × 5.87 formula for circular pools.
How long does it take to fill a pool with a garden hose?
A typical garden hose flows around 12 gallons per minute, or about 720 gallons per hour. A 15,000-gallon pool therefore takes roughly 20 hours of continuous flow. The fill-time result is based on that rate; higher pressure or a larger hose fills faster.
How much does pool water weigh?
Water weighs about 8.34 pounds per gallon, so a 20,000-gallon pool holds roughly 167,000 pounds - about 83 tons. That weight matters for above-ground pools and for any deck or structure near the pool.
Why is accurate volume important for chemicals?
Every pool chemical is dosed per a number of gallons. If your real volume is 18,000 gallons but you dose for 12,000, you under-treat and risk algae; dose for 25,000 and you over-treat, wasting product and irritating swimmers. The gallon figure here is the number to use on every chemical label.