Pond volume calculator
A pond 20 ft long, 10 ft wide and 3 ft deep on average holds 600 cubic feet of water, shown in US gallons and liters too. Measure at the waterline, average several depth readings, and use one figure for pumps, treatments and fill orders. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Length
- 20 ft
- Width
- 10
- Depth
- 3
- Volume ft3
- 600 ft
- Volume m3
- 16.9901079552
- Gallons
- 4,488.3116883117
- Liters
- 16,990.1079552
Garden ponds, wildlife ponds, koi ponds and farm watering holes all start with the same practical question: how much water is actually sitting in the hole you dug. This pond volume calculator answers it from three measurements every owner can take with a tape—length along the longest waterline, width across the shortest typical span, and average depth from several soundings—then returns US gallons and liters so liner quotes, pump curves, treatment doses and fill-truck orders share one number. The engine uses the rectangular pond identity volume equals length times width times average depth, converts cubic feet or cubic metres with exact legal constants, and rejects any dimension that is missing, zero, negative or not a finite number.
Measure length, width and average depth in one linear unit
Start at the waterline, not the excavated bank. Length is the longest surface distance you can stretch a tape across the pond; width is the distance at right angles to that, taken at the typical span rather than a tiny cove that would understate the basin.
Average depth is not the deepest hole and not the shallow planting shelf alone: walk or boat a simple grid, record depth at several points including margins and the deepest pocket, then take the arithmetic mean of those readings so the single depth field matches how pond retailers, koi keepers and agricultural extension charts already estimate fill. Send every linear number in one system. Mixing a metre length with a foot depth is invalid for this product: convert offline, then call once with a consistent set.
Length, width and depth must each be a strictly positive finite number. A kidney-shaped or free-form outline is still estimated as a rectangle of its bounding length and width; that is the landscaper shortcut this calculator implements on purpose. If you already have a surveyed surface area, you can still use this contract by treating length times width as that area and sending depth as the average water column.
Liner overlap, freeboard and seasonal drawdown mean full may sit below the coping—measure to the waterline you will actually hold, not only the excavated shell height.
How cubic volume becomes gallons and liters
The cubic volume of a rectangular pond is length times width times average depth in the unit you chose. When unit is ft, that product is cubic feet; when unit is m, it is cubic metres. Cubic feet convert to cubic metres with the exact international foot of 0.3048 metres, cubed.
US gallons use the legal identity that one US liquid gallon is exactly 231 cubic inches, so one cubic foot holds 1728 divided by 231 gallons. Liters use one thousand liters per cubic metre. Round-trip the numbers in tests: a twenty-by-ten-by-three-foot pond is six hundred cubic feet, and the gallon and liter fields are that cube converted with the constants above, not a rounded rule of thumb such as seven-point-five gallons per cubic foot.
Free-form kidney outlines, circular wildlife pools and stepped shelves are out of scope beyond the rectangular estimate; break an irregular plan into rectangles offline or use a surveyed area times average depth. Pair gallons with treatment labels that dose per thousand gallons, and pair liters with metric pump curves, without converting twice in your own code.
What you can do with it
Garden and koi pond fill estimates
Owners enter length, width and average depth to learn how many US gallons or liters they need before scheduling a fill truck, a hose fill, or a partial top-up after a leak.
Landscaper and retailer quotes
Dealers batch catalog pond sizes into gallons and liters for liners, pumps, UV clarifiers and treatment packages without retyping the rectangular volume formula.
FAQ
What happens if a dimension is zero or negative?
Zero or negative length, width or depth cannot define a physical pond and are not charged.
Should I use average depth or the deepest point?
Use average depth. Measure several soundings including shelves and the deepest pocket, then send that mean—the same practice used in koi, garden-centre and extension fill charts.
Is the pond volume calculator free?
The browser tool runs free on your device.
Does this handle kidney-shaped or circular ponds?
It estimates a rectangle of the bounding length and width times average depth, which is the standard tape-measure shortcut. Highly irregular or circular plans should be split into rectangles or use surveyed area times depth.
How many gallons are in one cubic foot of pond water?
One cubic foot holds 1728 divided by 231 US gallons, because a US liquid gallon is exactly 231 cubic inches. The calculator applies that for you and shows gallons and liters next to the cubic volume.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/build/pond \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"length":20,"width":10,"depth":3}'const res = await fetch("https://api.kit.forhosting.com/build/pond", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"length": 20,
"width": 10,
"depth": 3
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/build/pond",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"length": 20,
"width": 10,
"depth": 3
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/build/pond", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"length":20,"width":10,"depth":3}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"length":20,"width":10,"depth":3}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/build/pond", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"length": 20,
"width": 10,
"depth": 3
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "build.pond",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs | 1000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Successful API items cost $0.002; invalid input is not billed.
Measure length, width and average depth in one linear unit
The optional unit field accepts ft for feet, which is the default when omitted, or m for metres; aliases such as feet, foot, meters and metres map onto the same two choices. Zero, negative, empty, infinite and non-numeric values fail with invalid_input naming the field, and those failures are not charged.
How cubic volume becomes gallons and liters
Those constants never change between calls, so identical inputs always produce identical JSON: there is no network lookup, random seed or wall clock in the path. The response echoes length, width, depth and unit, then returns volume_ft3 and volume_m3 for engineering notes, gallons as US liquid gallons for retail and homeowner use, liters for metric dosing charts, the formula string length times width times average depth, and method always equal to pond_volume so downstream code can branch without sniffing field names. Zero or negative dimensions cannot define a physical pond and raise invalid_input.
API usage, pricing, liners, pumps and fill planning
Call the free in-browser pond volume calculator for backyard planning, garden-centre demos and classroom geometry checks without opening a spreadsheet. Remember that fish load, plant shelves and winter ice cover all care about the water you actually hold, so update average depth after a remodel or a drought drawdown rather than reusing last year’s number. Unlike a swimming-pool calculator that asks for kit shape, this pond tool is the three-tape estimate people search for when they have a garden basin, not a vinyl pool kit. Send a JSON body with required length, width and depth plus optional unit when dimensions are in metres. Use the prepaid API when a landscaping quote tool, koi-supply storefront, farm-pond estimator or marketplace configurator needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Pair this endpoint with liner-area helpers when you next estimate underlay and overlap, with pump-flow charts when you size turnover in gallons per hour against the volume you just computed, and with treatment calculators that dose per thousand gallons of pond water. Authors shipping SDKs can map gallons and liters straight into product copy while showing volume_ft3, volume_m3 and formula as explanatory detail for the buyer or the technician reviewing the job ticket.
Integration use cases
Apps and treatment dosing pipelines
Mobile and web apps recompute pond volume as users change depth, then feed gallons into per-thousand-gallon dose calculators under a stable prepaid API contract.
Technical questions
How do I calculate pond volume in gallons and liters?
Send JSON with length, width, average depth, and optional unit ft or m (feet is the default). The response includes gallons (US liquid), liters, volume_ft3 and volume_m3 from length × width × average depth.