Pond Volume Calculator
Knowing how many gallons a pond holds is the starting point for stocking fish, dosing treatments and sizing a pump. This calculator estimates the volume of a rectangular pond from three measurements you take in feet: the length, the width and the average depth. It multiplies the three to get the volume in cubic feet, then converts to US gallons using the standard factor of 7.48 gallons per cubic foot, which comes from 1,728 cubic inches in a cubic foot and 231 in a gallon. The average depth, not the deepest point, is what matters, because ponds slope and the maximum depth overstates the water held. Enter your own length, width and average depth to plan a stocking level, work out a safe dose of pond treatment, or check that a pump turns the water over often enough. For an irregular pond, average the length and width and treat it as a rectangle, or split it into sections, find each volume and add them. Always dose by measured gallons rather than guesswork to keep fish safe and treatments effective. Every figure here is computed deterministically from the rectangular volume formula, shown in full below, with a worked example that reconciles exactly to the calculator so you can follow each step.
Pond volume is length times width times average depth, converted to gallons: gallons = L x W x depth x 7.48. A 10 ft by 6 ft pond at 3 ft average depth holds 180 cubic feet, about 1,346.40 US gallons.
Pond volume formula
Volume (cu ft) = L x W x D
Gallons = Volume x 7.48
L = length (ft)
W = width (ft)
D = average depth (ft)
The product of length, width and average depth gives the cubic feet of water; multiplying by 7.48 converts that to US gallons.
Worked example
A rectangular pond 10 feet long, 6 feet wide, with an average depth of 3 feet.
- Volume = 10 x 6 x 3 = 180 cubic feet
- Convert: 180 x 7.48 = 1,346.40
- Volume = 1,346.40 US gallons
The pond holds about 1,346.40 gallons. These are the calculator's default inputs, so the result above matches the widget exactly.
Volume for common pond sizes (3 ft deep)
Each cubic foot of water is about 7.48 US gallons.
| Size (ft) | Cubic feet | US gallons |
|---|---|---|
| 6 x 4 | 72.00 | 538.56 |
| 10 x 6 | 180.00 | 1,346.40 |
| 12 x 8 | 288.00 | 2,154.24 |
| 16 x 10 | 480.00 | 3,590.40 |
Measurement units and conversion factors: US National Institute of Standards and Technology (NIST).
Pond volume calculator: frequently asked questions
How do I work out a pond's volume?
For a rectangular pond, multiply length by width by average depth to get the volume in cubic feet, then multiply by 7.48 to convert to US gallons. With a 10 by 6 foot pond, 3 feet deep, that is 180 cubic feet, which is about 1,346.40 gallons.
Why 7.48 gallons per cubic foot?
One US gallon is 231 cubic inches, and one cubic foot is 1,728 cubic inches. Dividing 1,728 by 231 gives about 7.48, so each cubic foot of water holds roughly 7.48 US gallons. This calculator uses that conversion factor.
What if my pond is an irregular shape?
Use the average depth and an average length and width to approximate it as a rectangle, which is usually close enough for stocking and treatment. For a more careful figure, split the pond into simpler rectangular or circular sections, find each volume, and add them up.
Why does pond volume matter?
Volume sets how much fish or plant stock the pond can support, how much dechlorinator or treatment to dose, and how to size a pump and filter. Dosing by gallons rather than guesswork keeps fish safe and chemicals effective.
Should I use average or maximum depth?
Use the average depth, not the deepest point. Ponds usually shelve and slope, so the maximum depth overstates the water held. Averaging the shallow and deep areas gives a volume much closer to the real amount of water.
Official sources
- Measurement units and volume conversion factors: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.