Pond Pump Size Calculator
Enter your pond volume and stocking to get the pump flow your pond needs for healthy turnover, plus the rated GPH to actually buy once head height and plumbing losses are factored in.
Not sure? Use the pond volume calculator first.
Leave at 0 if you have no waterfall. Roughly 1,000 to 1,500 GPH per foot of spillway width for a full sheet.
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target GPH
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turnover GPH
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rated GPH to buy
Buy a pump rated about GPH at your head height. Head height and plumbing reduce real flow, and the pump runs 24/7, so size up about 1.25 to 1.5 times your target and check the flow-versus-head curve. A koi pond should turn over at least once per hour, and because it runs continuously, energy use matters.
Right-sized pumps near GPH
Auto-matched to your rated flow. Confirm the flow-versus-head curve fits your lift before buying.
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How to Size a Pond Pump
Sizing a pond pump starts with two numbers: how many gallons your pond holds, and how fast you want to move that water. The standard target is turnover, the time it takes the pump to circulate the entire volume once. For a koi pond the goal is to turn the whole pond over at least once every hour, so you set your base flow equal to your gallons. A 1,200 gallon koi pond wants a base of at least 1,200 gallons per hour. Water gardens and goldfish ponds carry a lighter load and can turn over every two hours, which halves the base figure, while a heavily stocked koi pond benefits from circulating one and a half times per hour. The calculator above applies the right multiplier the moment you pick your pond type.
Add the Waterfall, Then Size Up
If your pond feeds a waterfall or stream, that feature draws its own flow on top of the turnover, so you add the waterfall GPH to your base before deciding what to buy. A rough guideline is 1,000 to 1,500 gallons per hour for every foot of spillway width to produce a full, satisfying sheet of water. Once you have a target that includes the waterfall, do not buy a pump rated at exactly that number. The flow printed on the box is measured at zero lift with no plumbing attached, which never matches a real installation.
Why Head Height Changes Everything
Head height is the vertical distance the pump has to lift water, from the pond surface to the top of the waterfall or the inlet of a raised filter. Every foot of lift, every elbow, every length of hose, and any UV clarifier in the line steals flow. A pump that claims 2,000 GPH at zero head might deliver only 1,200 once it is fighting 4 feet of rise and a run of pipe. That is why this calculator recommends a rated pump roughly 1.3 times your target, and why you should always read the manufacturer flow-versus-head curve. Find your real head on that curve and confirm the pump still delivers your target flow at that point, not at zero.
Energy Use Matters Because It Runs Nonstop
The pump is unique among pond gear because it runs 24 hours a day, every day, all year. That constant duty means a small difference in efficiency adds up to a real difference on your electric bill over a season. When you compare two pumps that both hit your target flow at your head height, choose the one that draws fewer watts to get there. Energy-efficient and asynchronous pumps, and variable-speed models that let you dial flow back during quiet hours, are worth the higher upfront price for a pump that never switches off. Avoid wildly oversizing, since a pump that far exceeds your turnover just blasts your koi, stirs debris, and wastes power around the clock for no benefit.
Keep going: size the rest of your pond.
Frequently Asked Questions
What size pump do I need for my pond in GPH?
Start with your pond volume in gallons and the turnover you want. A koi pond should turn over its entire volume at least once per hour, so a 1,000 gallon koi pond needs a pump moving at least 1,000 gallons per hour. Water gardens and goldfish ponds can turn over every two hours, while heavily stocked koi ponds benefit from one and a half times per hour. Add any waterfall flow on top, then buy a pump rated a little above that target to cover real-world losses.
Why should I buy a pump rated higher than my target GPH?
Because the number on the box is measured at zero lift with no plumbing. In a real pond the water has to climb the vertical height to your filter or waterfall, called head height, and push through hose, fittings, and a UV unit, all of which cut the actual flow. A pump rated for 2,000 GPH might only deliver 1,200 at 4 feet of head. Buying a pump rated about 1.25 to 1.5 times your target, and checking its flow-versus-head curve, keeps you from coming up short.
How often should a koi pond turn over?
A koi pond should circulate its whole volume at least once every hour. Koi are heavy-waste fish, so strong, constant flow keeps the water moving through your filter and UV, holds oxygen levels up, and prevents the dead spots where debris and gas collect. Lightly stocked water gardens can get by with turning over every two hours, but if you keep koi, size the pump so the GPH meets or exceeds your gallons. When in doubt, more turnover is the safer error.
What is head height and how do I measure it?
Head height is the total vertical distance the pump has to lift water, measured from the surface of the pond up to the highest point the water reaches, usually the top of your waterfall or the inlet of a raised filter. Measure that rise in feet. Long hose runs, elbows, and a UV clarifier add friction that behaves like extra head, so add roughly a foot of head for every ten feet of horizontal pipe. Match that total against the pump flow-versus-head curve.
Does a waterfall change the pump size I need?
Yes. A waterfall draws its own flow on top of the turnover your pond needs, so you add the waterfall GPH to your base figure. A common guideline is roughly 1,000 to 1,500 gallons per hour for every foot of spillway width to get a full sheet of water. If you enter a waterfall flow above, the calculator adds it to your turnover target before recommending a rated pump. For detailed spillway sizing, use our dedicated waterfall pump calculator.
Pond pumps run 24/7, so does energy use matter?
It matters a lot, because the pump is the one piece of pond equipment that runs continuously, day and night, all year. A poorly chosen pump can quietly become one of the largest electrical loads in the yard. Look for an energy-efficient or asynchronous pump, compare watts against the flow it delivers at your actual head height, and avoid oversizing far beyond your turnover target. A pump that hits your GPH while drawing fewer watts pays for itself over a season of constant running.
Should I oversize the pump to be safe?
Size up modestly, not wildly. Buying a pump rated about 1.25 to 1.5 times your target GPH covers head and plumbing losses without wasting electricity. Going far beyond that blasts your fish with too much current, stirs up debris, and burns power around the clock for no benefit. If you want flexibility, a pump with a flow valve or a variable-speed model lets you dial the flow back. Match the pump to the target this calculator gives you, then verify it on the flow-versus-head curve.