Calculate pool gallons from your pool shape, dimensions, and water depth. Pick how you want to measure depth, enter your numbers, and the calculator returns the water volume in gallons, liters, or cubic meters. The fill tools solve time, flow or volume. Water-loss tools relate a rectangular surface, level drop and observed lost volume, with average rates over an entered observation period.
Pool Gallon Formula
For an effectively constant footprint, volume is surface area multiplied by area-weighted average water depth. The calculator uses approximately 7.48051948 US gallons per cubic foot, derived from the exact foot and US-gallon definitions; 7.48 is a rounded shortcut.
Gallons = Area * AvgDepth * 7.48
For an even linear slope, the average depth is the mean of the shallow and deep depths. Use an area-weighted average or nonoverlapping rectangular sections for an uneven bottom:
AvgDepth = (Shallow + Deep) / 2
The surface area depends on the shape you select:
Rectangle: Area = Length * Width
Circle: Area = pi * (Diameter / 2)^2
Oval: Area = pi / 4 * Length * Width
Kidney estimate: Area ≈ (WidthA + WidthB) * Length * 0.45
Triangle: Area = Base * Height / 2
When you solve for fill time, the calculator divides the volume by the flow rate of your hose or pump:
FillTime = Volume / FlowRate
- Gallons = pool water volume in US gallons
- Area = surface area of the pool in square feet
- AvgDepth = average water depth in feet
- Shallow = depth at the shallow end
- Deep = depth at the deep end
- Length, Width = the two main horizontal dimensions
- Diameter = width of a round pool across the center
- WidthA, WidthB = the widest water span of each of the two kidney lobes
- Base, Height = the base and perpendicular height of a triangular pool
- 7.48 ≈ US gallons per cubic foot (rounded)
- Volume = known pool volume used for the fill time mode
- FlowRate = water delivery rate of your source
The shape selector sets which area formula is used and shows only the inputs that shape needs. The depth input lets you give one average depth or separate shallow and deep depths, which the calculator averages for you. The unit selectors convert your entries to a common base before the math runs, so you can mix measurement habits and still read the answer in gallons, liters, or cubic meters. The fill time mode skips the geometry and works straight from a volume and a flow rate.
Typical Pool Sizes and Volumes
These figures assume an average depth of about 5 feet and are useful for a quick sanity check against your own result.
| Pool size and shape | Approximate gallons |
|---|---|
| 12 ft round | 4,230 |
| 24 ft round | 16,921 |
| 15 x 30 ft rectangle | 16,800 |
| 20 x 40 ft rectangle | 29,900 |
| 16 x 32 ft oval | 15,000 |
To convert a result between units, use these factors.
| Conversion | Value |
|---|---|
| 1 cubic foot | 7.48 US gallons |
| 1 US gallon | 3.785 liters |
| 1 cubic meter | 264.2 US gallons |
Example Calculations
A rectangular pool is 16 feet wide and 32 feet long, with a shallow end of 3 feet and a deep end of 8 feet. The average depth is (3 + 8) / 2 = 5.5 feet. The area is 16 * 32 = 512 square feet. Using the conversion-based factor, the volume is approximately 512 * 5.5 * 7.48051948 = 21,065.14 US gallons.
A round pool has a 21-foot diameter and an average depth of 4 feet. The area is pi * (21 / 2)^2 = 346.4 square feet. Using the unrounded circular area and conversion-based factor, the volume is approximately 10,363.83 US gallons. At 9 US gallons per minute, the fill time is approximately 1,151.54 minutes, or 19.19 hours.
FAQ
Why is the average depth used instead of the deep end? The deep end only describes part of the pool. Using the deep depth everywhere would overstate the volume. For an even linear slope, the end-depth mean represents the average. With shelves, changing slopes or irregular depths, use an area-weighted average or nonoverlapping rectangular sections.
How accurate is the result for an irregular pool? The kidney formula is an empirical approximation with no fixed accuracy guarantee. Triangle geometry applies to a genuinely triangular water footprint; irregular curves, steps and benches need more detailed measurement. Verify capacity before chemical dosing.
How do I get the volume in liters or cubic meters? For pool volume or a volume solve, choose Volume result unit in Optional settings before Calculate. Results also show US gallons, liters and cubic meters together. Input unit changes convert the current numeric quantity; changing the section measurement unit reinterprets the section numbers.
