Cubic feet to gallons converter
One cubic foot is about 7.480519480519 US gallons: convert a tank, aquarium, pool or rain barrel measured in cubic feet into US liquid gallons, with the exact factor instead of the 7.48 shortcut. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Cubic feet
- 1
- Result
- 7.4805194805 US gal
- Converted
- 7.4805194805
- Us gallons
- 7.4805194805
- Gallons
- 7.4805194805
A cubic-feet-to-gallons converter turns an imperial volume in cubic feet into US liquid gallons—the unit used for aquarium fills, pool chemistry notes, rain barrel estimates, shipping liquid capacity, and many US residential water rules of thumb. Approximate mental shortcuts such as multiply by seven point four eight are rejected in favour of that exact fraction, so homework checks and product tables match engineering definitions.
Why cubic feet and US liquid gallons meet at 1728 over 231
Cubic feet remain common on US construction take-offs, tank nameplates that quote internal volume in feet, shipping and crate notes, and residential rules of thumb for basements, crawl spaces, and bulk storage. US liquid gallons are the everyday unit for aquarium water, pool fill estimates, rain barrels, heating oil notes, and many municipal water communications aimed at households.
The bridge between them is exact under US customary liquid definitions: one international foot is twelve inches, so one cubic foot is twelve cubed—one thousand seven hundred twenty-eight cubic inches—and one US liquid gallon is defined as exactly two hundred thirty-one cubic inches.
That makes the conversion a single exact multiplication, US gallons equals cubic feet times one thousand seven hundred twenty-eight divided by two hundred thirty-one, which reduces to five hundred seventy-six over seventy-seven, or about seven point four eight zero five one nine four eight zero five one nine gallons per cubic foot. Teachers and estimators often still teach the rough rule of thumb multiply by seven point four eight, but that introduces a scale error that shows up on a large cistern or a whole-building liquid capacity.
Practical tips, checks, and related searches
Prefer sending bare numbers when you control the client; string numbers are accepted only when they match a strict finite numeric pattern without units, thousand separators, or currency symbols. Round-trip sanity checks are easy: convert a known textbook value such as one cubic foot and confirm you receive approximately seven point four eight zero five one nine four eight zero five one nine US gallons after rounding, or convert ten cubic feet and confirm the result is ten times that factor.
When teaching, pair the exact path with the mental shortcut multiply by seven point four eight so students see the drift on large tanks. Stay inside the absolute range so the multiplication cannot overflow into a non-finite result the solver must reject.
This landing targets people searching for cubic feet to gallons, ft3 to gallons, or convert cubic feet to US gallons with an exact factor calculator; it is not a general multi-unit volume hub, not a gallons-to-cubic-feet primary form, not a litres tool, and not an imperial UK gallon converter. Prefer this capability when the input is already in cubic feet and you only need US liquid gallons; if you must convert among many units in one call, use a broader volume converter instead.
What you can do with it
Aquarium and pond fill estimates
Turn tank or pond volumes quoted in cubic feet into US gallons for water-change planning, dechlorinator dosing, and heater sizing tables with the same exact factor every row.
Pool and rain-barrel capacity checks
Homeowners and landscapers convert cubic-foot cistern or pool dimensions to US gallons and compare hand work against deterministic steps before ordering treatments.
FAQ
What formula converts cubic feet to US gallons?
US gallons = cubic feet × (1728 ÷ 231). One cubic foot is exactly 1728 cubic inches; one US liquid gallon is exactly 231 cubic inches.
Is 1728/231 exact or approximate?
Exact under US liquid customary definitions. This tool uses 1728/231 (about 7.480519480519 gal per ft³), not a rough multiply-by-7.48 estimate and not the imperial UK gallon.
Can I convert US gallons back to cubic feet?
This capability is cubic feet → US gallons only. Divide gallons by 1728/231 on your side, or use a bidirectional volume converter for other units.
Is the cubic feet to gallons converter free?
The browser tool is free and runs locally.
Why doesn't one cubic foot give a round number of gallons?
Because a cubic foot holds 1,728 cubic inches and a US gallon holds 231, and 1,728 does not divide evenly by 231. The result, about 7.480519480519 gallons, is rounded only for display, while the conversion uses the exact ratio.
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/conv/cubic-feet-to-gallons \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"cubic_feet":1}'const res = await fetch("https://api.kit.forhosting.com/conv/cubic-feet-to-gallons", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"cubic_feet": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/cubic-feet-to-gallons",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"cubic_feet": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/cubic-feet-to-gallons", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"cubic_feet":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"cubic_feet":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/cubic-feet-to-gallons", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"cubic_feet": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.cubic_feet_to_gallons",
"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.
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
Invalid or missing input fails with a clear invalid_input error instead of inventing a number.
How to call the API and what comes back
Absolute values must stay within the published limit of one trillion. Send a JSON body with one required finite number field named cubic_feet. Aliases ft3, ft³, cu_ft, cuft, value, volume, feet_cubed, and cubic_ft are accepted so SDK clients and form posts can use the name that fits the product. On success the response echoes rounded cubic_feet, sets us_gallons, gallons, result, and converted to the same rounded US-gallon magnitude, unit to the token US gal, from_unit to ft³ and to_unit to US gal, factor to the rounded ratio one thousand seven hundred twenty-eight over two hundred thirty-one, cubic_inches_per_cubic_foot to one thousand seven hundred twenty-eight, cubic_inches_per_us_gallon to two hundred thirty-one, formula to the string us_gallons equals cubic_feet times open parenthesis one thousand seven hundred twenty-eight divided by two hundred thirty-one close parenthesis, message to a short English summary, and steps to an ordered array of substitution lines. Failed validation—missing fields, non-finite numbers, bare plus or minus signs, non-numeric strings, values outside absolute limits, or a non-finite converted result—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.
Practical tips, checks, and related searches
Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately omit cubic_feet or pass text.
Integration use cases
Homework and unit-test fixtures
Students and engineers convert classroom cubic-foot readings to US gallons and pin golden JSON so browser and API arithmetic never drift.
Technical questions
What happens on missing or non-numeric input?
The API returns invalid_input naming the problem (for example a missing cubic_feet field). Failed tasks are not charged.