Pool Volume Calculator
Calculate pool water volume in gallons or litres.
Project details
Enter your measurements below.
Average depth makes a useful pool estimate—when the shape is reasonably simple
Pool volume is easy to underestimate because the water depth changes across the basin. DIYGauge averages the shallow and deep measurements, multiplies that average by the surface area for the selected shape, and converts the resulting volume into gallons or litres. The method works well as a planning estimate for rectangular, round and oval pools with a reasonably gradual floor profile. Steps, benches, spas, tanning ledges, freeform curves and abrupt deep wells can make the real volume different. That difference matters most when the number will be used for chemical treatment, so verify a safety-sensitive volume with reliable pool records, metering or professional guidance rather than relying on geometry alone.
Rectangular, round and oval plan shapes using an average of shallow and deep depth.
Cubic feet are converted to gallons using approximately 7.48052 gallons per cubic foot.
Irregular shelves, spas and compound floor shapes are not represented by one simple average-depth model.
How to use the Pool Volume Calculator
- Choose the pool shape that best matches the main water body: rectangular, round or oval.
- Measure inside water dimensions rather than the outside deck or coping dimensions.
- Measure shallow and deep water depth, then let the calculator use their average for the simplified volume model.
- Use the result for planning fill time, water use or general capacity; verify the number independently before safety-sensitive chemical dosing.
What average depth assumes about the pool floor
A simple average treats the transition from shallow to deep as reasonably even. It does not model the volume displaced by large steps, benches, attached spas or complex freeform geometry.
Use the estimate according to how accurate the decision needs to be
For rough water-use, refill-time or operating estimates, the geometric result is often useful. For chemical dosing or another decision where a substantial volume error could matter, compare it with the pool builder's specification, a known meter reading or another reliable source.
Worked example: 30 × 15 ft rectangular pool with a 3.5–7.5 ft depth range
- Pool size
- 30 ft × 15 ft
- Shallow depth
- 3.5 ft
- Deep depth
- 7.5 ft
- Average depth
- 5.5 ft
The surface area is 450 sq ft. Multiplying by the 5.5 ft average depth gives 2,475 cu ft. At about 7.48052 gallons per cubic foot, the simplified estimate is roughly 18,514 gallons. Large steps, benches or an attached spa would make the actual water volume lower or different from this simple basin estimate.
Practical planning tips
Measure water depth from the water surface to the pool floor, not from the coping or deck level.
For a pool with a distinct shallow shelf or separate deep well, calculate major sections separately when possible instead of forcing one average over the entire basin.
Keep an older builder specification or water-meter fill record if available; it can be a better reference than repeating geometry measurements later.
When using the volume to estimate fill time, measure actual hose or supply flow rather than assuming a standard gallons-per-minute rate.
Common mistakes to avoid
Using the deepest point as the depth for the entire pool, which can substantially overstate water volume.
Measuring outside dimensions that include coping, walls or deck rather than the internal water footprint.
Treating an oval or freeform pool as a full rectangle because its maximum length and width are easy to measure.
Using an approximate geometric result for precise chemical dosing without checking the pool's actual or documented volume.
Pool Volume Calculator FAQs
Why does the calculator average shallow and deep depth?+
For a pool floor that slopes reasonably steadily, the average depth is a practical way to estimate total volume without mapping every point on the floor.
How many gallons are in one cubic foot of pool water?+
The calculator uses approximately 7.48052 US gallons per cubic foot for the conversion.
Will steps and benches change the result?+
Yes. They displace water and can make the true volume lower than a simple full-basin calculation. Large features should be accounted for separately when accuracy matters.
Is this accurate enough for pool chemicals?+
Treat it as an estimate. Chemical treatment can be safety-sensitive, so verify pool volume from reliable records, metering or qualified pool guidance before relying on the number for dosing.