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FurCalc

Pond Volume Calculator β€” Gallons, Liner Size, Pump & Stocking

Calculate pond volume for rectangular, round or irregular shapes. Includes pond-liner size (with overhang allowance) and pump flow rate recommendation.

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Koi need minimum 3 ft depth; 4+ ft for cold climates (prevent freezing).

Pond volume
1,346US gallons
5,096 L Β· Water weight β‰ˆ 11,236 lb
Pond liner size
18β€² Γ— 14β€²
Includes 2 ft overhang
Pump flow
1346–2693 GPH
1–2Γ— turnover/hr
Koi: 500 gal per fish. Goldfish: 50 gal per fish. Add UV clarifier for green water prevention.

Frequently Asked Questions

How do I calculate pond volume in gallons?

Rectangular: L Γ— W Γ— D Γ— 7.48 (cubic feet to gallons). Round: Ο€ Γ— rΒ² Γ— D Γ— 7.48. Irregular shapes: use the rectangular formula Γ— 0.75 as approximation.

How deep should a koi pond be?

Minimum 3 feet; 4+ feet recommended for cold climates (prevents freezing solid and gives koi a thermal refuge). Shallower ponds risk overheating in summer and ice damage in winter.

How big a liner do I need?

Liner dimensions: length + 2Γ—depth + 2 ft overhang, by width + 2Γ—depth + 2 ft. Always buy EPDM or 45 mil PVC β€” cheaper liners degrade in UV within 3–5 years.

What pump size do I need for my pond?

Turn over the entire volume 1–2Γ— per hour. A 1,000 gal pond needs a 1,000–2,000 GPH pump. For heavy fish loads or water features, use 2Γ— turnover.

How many fish can a pond hold?

Koi: 500 gal per adult fish (they grow 2–3 ft). Goldfish: 50 gal per fish. Mosquitofish: 2 gal per fish. Overstocking leads to disease and poor water quality.

Sources & References

  1. [1]
    Backyard Pond Planning Guide β€” Pond Trade Magazine
  2. [2]
    Aquascape Pond Design β€” Aquascape
  3. [3]

Common mistakes to avoid

  • Measuring after a rain β€” depth inflated. Wait for stable water level.
  • Ignoring plant displacement β€” heavily planted ponds hold 20-30% less water than geometric volume.
  • Treatment dosed by surface area instead of volume β€” most pond medications are volume-based.

Pro tips

  • For irregular shapes: measure length Γ— width Γ— depth at 3-5 spots, average them.
  • Add 15% buffer to calculated volume for piping, skimmer, waterfall reservoir.
  • Stock koi: 250-500 gallons per adult (24-36 inches).