Pond Volume Calculator
Gallons = length × width × average depth (ft) × 7.48052. A 9 × 6 ft pond 2 ft deep holds 108 ft³, or 807.9 gal; its liner is 15 × 12 ft. Liner = each side + twice the deepest point + 2 ft of edge in all: 9 + 4 + 2 = 15 ft.
Pond volume
807.9 gal
3,058 liters · US gallons
- Liner size
- 15 ft × 12 ft
- Cubic feet
- 108 ft³
- Cubic meters
- 3.06 m³
US gallons. One imperial (UK) gallon is about 1.2 US gallons.
Checked by the Yardstick Math team · How we check
Worked examples
A 9 × 6 ft pond, 2 ft deep
- 9 × 6 × 2 = 108 ft³
- 108 × 7.48052 = 807.9 gal (Gardenponds: “approx. 807”)
- 108 ft³ = 3.058 m³ = 3,058 L
- Liner length: 9 + 2 × 2 + 2 = 15 ft
- Liner width: 6 + 2 × 2 + 2 = 12 ft
Result: 807.9 gal (3,058 L); liner 15 × 12 ft.
Checked by the automated test “pond — 9 × 6 × 2 ft → 108 ft³ = 807.9 gal, 3,058 L, liner 15 × 12 ft”.
A round pond 8 ft across, 2 ft deep
- Radius 4 ft: 3.1416 × 4² = 50.27 ft²
- 50.27 × 2 = 100.53 ft³
- 100.53 × 7.48052 = 752 gal
- Liner: 8 + 2 × 2 + 2 = 14 ft each way
Result: 752 gal; liner 14 × 14 ft.
Checked by the automated test “pond — circle 8 ft across, 2 ft deep → 100.53 ft³ = 752 gal, liner 14 × 14 ft”.
How it works
Volume (ft³) = length × width × average depth (rectangle); 3.1416 × radius² × depth (circle); 3.1416 × half-length × half-width × depth (oval)
US gallons = ft³ × 7.48052, from 1 ft³ = 1,728 in³ and 1 US gallon = 231 in³ exactly (NIST Handbook 44); the pond sources round it to 7.481 and 7.48
Liters = m³ × 1,000
Liner = (length + 2 × deepest point + 2 × edge) × (width + 2 × deepest point + 2 × edge)
Assumptions
- Gardenponds: “Multiply the length x the width x the depth x 7.481”; CenterPoint Pond: “Length x Width x Depth x 7.48 = Pond Gallons”.
- The volume uses the average water depth (CenterPoint Pond: “Use average measurements in feet”): with plant shelves it is less than the deepest point.
- The liner uses the deepest point and 1 ft of edge on each side (Gardenponds: “plus 2' for an adequate edge”).
- US gallons. Both pond sources are suppliers; the 7.48052 factor comes from NIST's definitions, 1,728 ÷ 231.
- For a round pond CenterPoint Pond rounds to 3.14 and 7.5: 754 gal for the 8 ft example below, against 752 gal with the exact factors.
Reference table
| Pond | 1.5 ft deep | 2 ft deep | 3 ft deep |
|---|---|---|---|
| 6 × 9 ft | 606 | 808 | 1,212 |
| 8 × 10 ft | 898 | 1,197 | 1,795 |
| 10 × 12 ft | 1,346 | 1,795 | 2,693 |
| 12 × 16 ft | 2,154 | 2,873 | 4,309 |
ft³ × 7.48052, rounded to the nearest gallon.
Before you dig
- Average depth. Measure the water depth at several points and average them; shelves count.
- Deepest point. Type it apart: the liner follows the deepest point, the volume the average.
Common mistakes
- Using the deepest point for the volume With plant shelves, a pond 2 ft at its deepest may average 1.5 ft: a 9 × 6 ft pond then holds 606 gal, not 808.
- Counting the depth once in the liner The liner goes down and up both walls: add twice the deepest point, then the edge. A 9 ft pond 2 ft deep needs 15 ft, not 13.
- Mixing gallons and liters ft³ × 7.48052 gives US gallons. For liters, multiply m³ by 1,000, or ft³ by 28.32 (NIST: 1 ft³ = 28.3168 L).
- US or imperial gallons A UK pump or treatment label may use imperial gallons: NIST puts the British gallon at 1.201 US gallons, so 807.9 US gal is about 673 imperial gallons.
Frequently asked questions
How many gallons is my pond?
Length × width × average depth in feet × 7.48052: a 9 × 6 ft pond 2 ft deep holds 108 ft³, 807.9 gal. Use the average depth if the pond has shelves.
How many liters is my pond?
Length × width × average depth in meters × 1,000: a 3 × 2 m pond 0.6 m deep holds 3.6 m³, 3,600 L.
How to calculate pond volume?
Multiply the surface by the average depth: length × width for a rectangle, 3.1416 × radius² for a circle, 3.1416 × half-length × half-width for an oval. Then ft³ × 7.48052 = US gallons.
How to calculate pond liner size?
Liner length = pond length + 2 × deepest point + 2 ft of edge; same for the width (Gardenponds). A 9 × 6 ft pond 2 ft deep needs a 15 × 12 ft liner.
How big of a pond liner do I need?
Each side + twice the deepest point + 2 ft: a round pond 8 ft across and 2 ft deep needs a 14 × 14 ft liner.
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- Pond calculations — Gardenponds.com, accessed
- Pond Formulas — CenterPoint Pond, accessed
- Handbook 44, Appendix C – General Tables of Units of Measurement — NIST, accessed