How Big Should a Koi Pond Be? Gallons for Every Common Pond Size
Short answer: a koi pond should hold at least 1,000 gallons and be at least 3 ft deep, with about 250 gallons per adult koi as the tight limit and 500 gallons per koi as the comfortable one. An 8 × 6 ft pond that is 3 ft deep holds 1,077 gallons, so it fits 4 koi at the tight limit or 2 at the comfortable one.
Koi pond size chart: rectangular ponds
Every row is computed with length × width × depth × 7.48. Koi counts are rounded down. The liner is the size to buy: pond length + 2 × depth + 2 ft, same for the width.
| Pond (ft) | Gallons | Liner (ft) | Koi at 250 gal | Koi at 500 gal |
|---|---|---|---|---|
| 6 × 4 × 3 | 539 | 14 × 12 | 2 (too small for koi) | 1 |
| 8 × 5 × 3 | 898 | 16 × 13 | 3 (under 1,000) | 1 |
| 8 × 6 × 3 | 1,077 | 16 × 14 | 4 | 2 |
| 10 × 6 × 3 | 1,346 | 18 × 14 | 5 | 2 |
| 10 × 8 × 3 | 1,795 | 18 × 16 | 7 | 3 |
| 12 × 8 × 3 | 2,154 | 20 × 16 | 8 | 4 |
| 12 × 10 × 3 | 2,693 | 20 × 18 | 10 | 5 |
| 15 × 10 × 3 | 3,366 | 23 × 18 | 13 | 6 |
| 16 × 12 × 4 | 5,745 | 26 × 22 | 22 | 11 |
| 20 × 12 × 4 | 7,181 | 30 × 22 | 28 | 14 |
| 20 × 15 × 4 | 8,976 | 30 × 25 | 35 | 17 |
Round koi ponds
| Diameter × depth (ft) | Gallons | Liner (ft, square) | Koi at 250 gal | Koi at 500 gal |
|---|---|---|---|---|
| 6 × 3 | 634 | 14 × 14 | 2 (too small for koi) | 1 |
| 8 × 3 | 1,128 | 16 × 16 | 4 | 2 |
| 10 × 3 | 1,762 | 18 × 18 | 7 | 3 |
| 12 × 3 | 2,538 | 20 × 20 | 10 | 5 |
| 14 × 4 | 4,606 | 24 × 24 | 18 | 9 |
| 16 × 4 | 6,016 | 26 × 26 | 24 | 12 |
How many gallons do you need for the number of koi?
| Koi | Tight (250 gal each) | Comfortable (500 gal each) |
|---|---|---|
| 3 | 750 (use 1,000 minimum) | 1,500 |
| 4 | 1,000 | 2,000 |
| 6 | 1,500 | 3,000 |
| 10 | 2,500 | 5,000 |
| 20 | 5,000 | 10,000 |
Plan for the adult size, not the 4 inch fish you buy. Koi reach 2 to 3 ft, so a pond that suits six small koi can be crowded in a few years.
Irregular ponds hold less than the chart says
The tables assume straight sides. A natural shaped pond with sloped edges holds about 10 percent less: the factor is 6.7 instead of 7.48. For example, 10 × 6 × 3 ft is 1,346 gallons as a box but about 1,206 gallons as a curved pond. Use the calculator below to switch shape.
Pump and depth
- Pump: move the full pond volume once an hour. A 1,795 gallon pond needs a pump rated 1,800 gallons per hour or more at the height it lifts the water, plus extra for a waterfall.
- Depth: 3 ft is the usual minimum quoted for koi. In cold winters, deeper (4 ft or more) gives the fish a stable layer at the bottom.
Measure, then check the exact number for your pond with the calculator. For fish in tanks instead, see the aquarium calculator.
Sources: the 250 gallons per koi, 1,000 gallon and 3 ft figures are pond-builder rules of thumb (for example Koi Kompanion and Premier Pond guides); there is no official standard, and keepers often go higher. All gallons, liner sizes and koi counts are calculated with the formulas above.
Try the pond volume calculator
Enter your own numbers below, or open the full pond volume calculator with the formula and more examples.
This guide is general information, not veterinary advice. Your pet may differ: ask your vet. Terms
Frequently asked questions
How many gallons does a koi pond need?
At least 1,000 gallons and 3 ft deep. That fits about 4 adult koi at the tight limit of 250 gallons each, or 2 at a comfortable 500 gallons each.
How many koi can I keep in a 1,000 gallon pond?
About 4 at 250 gallons per koi, or 2 at 500 gallons per koi. A pond 8 × 6 × 3 ft holds 1,077 gallons.
What size liner do I need for a koi pond?
Pond length + 2 × depth + 2 ft by pond width + 2 × depth + 2 ft. A 10 × 8 × 3 ft pond needs 18 × 16 ft.
How deep should a koi pond be?
At least 3 ft. Colder winters call for 4 ft or more.
How do I calculate koi pond gallons?
Length × width × average depth in feet × 7.48 for a box shaped pond, or × 6.7 for a curved pond.