Pond and Pool Water Volume Calculator

Estimate pond or pool capacity for filling and routine maintenance.

Inputs

Preset: 10x6 ft pond volume

A 10 by 6 ft water surface with 2 ft average filled depth, equivalent to 120 ft³. Use actual average water depth and adjust for shelves or irregular shapes.

Water volume - Length (ft), Width (ft), Average water depth (ft)
Enter length in ft.
Enter width in ft.
Enter average water depth in ft.
Formula, inputs and conditions

Formula: Length*Width*Average water depth*1728/231

Decimal results are displayed to two places when needed.

Inputs
Horizontal plan dimensions and a representative average water depth.
Outputs
Cubic feet and U.S. gallons.
Conditions and scope
The dimension-based method assumes a rectangular footprint and average filled water depth. Measure irregular basins in sections or use a separately established volume. Results are planning estimates, not engineering, permit, code or contractor-price decisions.

Use average filled depth for water volume

A rectangular pond or pool volume is footprint area times average filled water depth. Maximum excavation depth can overstate the water volume when there are shelves, slopes or unfilled freeboard. US gallons are a unit conversion from the resulting cubic feet.

Measure and calculate

  1. Measure the water surface length and width for the rectangular approximation.
  2. Enter average filled water depth in feet.
  3. Use the cubic-foot conversion mode if you already know the actual volume.
Calculation method

US gallons = length × width × average depth × 1,728 ÷ 231.

A worked example

Inputs
The water footprint is 10 by 6 ft with 2 ft average filled depth.
Calculation
Volume: 10 × 6 × 2 = 120 ft³. US gallons: 120 × 1,728 ÷ 231 = 897.6623.
Result
897.66 USgal

The estimate is 897.66 US gallons. For an irregular basin, calculate measured sections or use an independently determined volume instead of treating maximum dimensions as a full rectangle.

Read the result

Output interpretation and next steps
Output or checkWhat it means for your project
Water volume: US galThe rectangular approximation multiplies the water footprint by average filled depth, then converts ft³ to US gallons.
Average versus maximum depthShelves, slopes and unfilled space make maximum excavation depth unsuitable as average water depth. An irregular basin needs measured sections or another volume estimate.

Common questions

Should I enter excavation depth or water depth?

Use average filled water depth. Empty space above the waterline is not part of the stored water volume.

Are these imperial gallons?

No. The conversion uses US liquid gallons, with 231 cubic inches per gallon.