Gallons to cubic feet converter
Turn US gallons into cubic feet with the exact definition: 1 gallon is 0.133680555556 ft³, because a gallon holds 231 cubic inches and a cubic foot 1728. Handy for comparing a tank with a room, a crate or a freight cube. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Gallons
- 1
- Result
- 0.1336805556 ft³
- Converted
- 0.1336805556
- Cubic feet
- 0.1336805556
- From unit
- gal
Enter a finite non-negative volume in US gallons; the tool multiplies by the exact customary definition that one US liquid gallon equals 231 cubic inches and one international cubic foot equals 1728 cubic inches, so cubic feet equals gallons times 231 divided by 1728. Approximate mental shortcuts such as multiply by 0.134 are unnecessary here because the ratio is exact by definition of the US liquid gallon and the international foot, not a survey constant that needs estimation.
Why US gallons convert to cubic feet at exactly 231/1728
Gallons remain everyday liquid volume across the United States for fuel drums, milk jugs, paint cans, aquarium fills, and water tanks, while cubic feet dominate HVAC nameplates, crate cubes, room-air rules of thumb, and many construction take-offs that still mix customary volume with linear drawings in feet.
Drivers comparing a tank listed in gallons to a room or enclosure listed in cubic feet, shippers converting drum capacity into freight cubes, chemists checking bulk stock against a tank plate, and students solving unit-conversion homework all need a single reliable bridge from US gallons to cubic feet. That bridge is definitional rather than approximate: one US liquid gallon is exactly 231 cubic inches, and the international foot is exactly twelve inches, so one cubic foot is exactly 1728 cubic inches.
Conversion is therefore a single exact multiply—cubic feet equals gallons times 231 divided by 1728—with no leftover uncertainty and no dependence on temperature corrections or local survey feet. This landing stays on the US liquid path only. It does not convert imperial UK gallons, which are larger and would mislead searchers who typed gallons to cubic feet for US tanks or kitchen volumes, and it does not convert dry gallons used for some bulk commodities.
Zero gallons maps cleanly to zero cubic feet. Negative volumes are rejected because a physical volume is nonnegative; signed deltas belong in a different tool.
Practical tips, checks, and related searches
Round-trip sanity checks are easy: convert one gallon and confirm you receive 231 divided by 1728 cubic feet after twelve-decimal rounding, convert 1728 divided by 231 gallons—about 7.480519480519 gallons—and confirm you receive one cubic foot after rounding, or convert zero and confirm zero. When teaching, show that multiplying the published cubic feet by 1728 and dividing by 231 recovers the original gallons within the same twelve-decimal rounding used for published fields. Stay inside the absolute range so the multiply cannot overflow into a non-finite result the solver must reject.
This landing targets people searching for gallons to cubic feet, convert US gallons to ft3, or an exact 231-over-1728-factor calculator; it is not a general multi-unit volume hub, not a cubic-feet-to-gallons primary form, not an imperial gallon converter, and not a litres path. Prefer this capability when the input is already in US gallons and you only need cubic feet; if you must convert among many volume units in one call, use a broader unit converter instead.
When sizing an HVAC tank or a shipping crate, remember that this tool converts volume only and does not convert mass, density, or flow rate—use a dedicated density or flow converter for those. Keep requests small, pin the rounded cubic-foot value in tests, and you get reproducible results for homework, LMS plugins, and automation scripts without standing up a computer-algebra system of your own.
What you can do with it
HVAC tanks and room-air notes
Convert a US gallon tank rating into cubic feet so it sits on the same scale as HVAC nameplates, room-air rules of thumb, and duct-volume take-offs.
Shipping cubes and bulk drums
Turn US drum gallons into freight cubes for bills of lading, crate fill, and warehouse slotting that store capacity in cubic feet.
FAQ
What formula converts gallons to cubic feet?
Cubic feet = gallons × 231 / 1728. One US liquid gallon is exactly 231 cubic inches and one cubic foot is exactly 1728 cubic inches, so the factor is exact, not an estimate.
Is the factor 231/1728 exact?
Yes. The US liquid gallon is defined as 231 cubic inches, and the international foot is exactly 12 inches, so 1 ft³ = 1728 in³. This tool multiplies by 231/1728 only.
Does this convert imperial (UK) gallons?
No. It converts US liquid gallons to cubic feet only. An imperial gallon is larger and is not accepted as input on this landing.
Is the gallons to cubic feet converter free?
The browser tool is free and runs locally.
How many gallons fit in one cubic foot?
About 7.480519480519 US gallons. That is 1728 divided by 231, so entering that many gallons gives back exactly one cubic foot after rounding, a quick way to check the conversion.
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/gallons-to-cubic-feet \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"gallons":1}'const res = await fetch("https://api.kit.forhosting.com/conv/gallons-to-cubic-feet", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"gallons": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/conv/gallons-to-cubic-feet",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"gallons": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/conv/gallons-to-cubic-feet", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"gallons":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"gallons":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/conv/gallons-to-cubic-feet", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"gallons": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "conv.gallons_to_cubic_feet",
"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 | 1000000000000 |
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, negative, or missing input fails with a clear invalid_input error instead of inventing a number.
How to call the API and what comes back
The value must be greater than or equal to zero and must stay within the published limit of one trillion. Send a JSON body with one required finite nonnegative number field named gallons. Aliases gal, gallon, value, volume, us_gallons, and gallons_value are accepted so SDK clients and form posts can use the name that fits the product. On success the response echoes rounded gallons, sets cubic_feet, result, and converted to the same rounded cubic-foot magnitude, unit to the token ft³, from_unit to gal and to_unit to ft³, factor and cubic_feet_per_gallon to 231 divided by 1728 after twelve-decimal rounding, cubic_inches_per_gallon to 231, cubic_inches_per_cubic_foot to 1728, formula to the string cubic_feet equals gallons times 231 divided by 1728, message to a short English summary, and steps to an ordered array of substitution lines that show the exact US liquid definition. Failed validation—missing fields, non-finite numbers, negative volumes, 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 no extra unit tariff. Prefer sending bare JSON numbers when you control the client; numeric strings are accepted only when they match a strict finite numeric pattern without unit symbols, thousand separators, or currency marks attached to the value.
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 gallons or pass text placeholders while debugging their client code.
Integration use cases
Homework and unit-test fixtures
Students and engineers convert classroom gallon volumes to cubic feet and pin golden JSON so browser and API arithmetic never drift.
Technical questions
What happens on missing, negative, or non-numeric input?
The API returns invalid_input naming the problem (for example a missing gallons field or a negative volume). Failed tasks are not charged.