Well volume calculator
A 6-inch well with 100 feet of standing water holds about 146.88 US gallons. Enter the casing's inside diameter and the water column to know what sits in the well before you size a pump or mix a chlorine dose. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Diameter
- 6
- Depth
- 100
- Gallons
- 146.879657
- Cubic feet
- 19.634954
A drilled water well is almost always a vertical cylinder: a steel or PVC casing of a known inside diameter standing over a column of water whose depth you can measure with a tape, an e-line, or a pressure transducer. This well volume calculator turns those two field numbers — casing diameter in inches and standing water depth in feet — into the volume of water currently stored in the well, reported in US liquid gallons. The geometry is the school cylinder: the circular cross-section times the height of the water column, converted with the exact legal identity that one US gallon is two hundred thirty-one cubic inches.
Where a well volume calculator belongs in daily work and software
Private well owners meet this calculation when a static-level tape, a casing stamp, and a notebook are enough to decide how many gallons sit in the hole before a pump is sized or a bleach dose is mixed. Drillers and pump installers use it on the truck to convert a six-inch or eight-inch log into a volume that a recovery test or a shock-chlorination worksheet can consume without opening a general geometry textbook.
County sanitarians and well-permit reviewers use it to check that a reported water column and casing size imply a plausible storage figure rather than a transposed digit. Students and earth-science teachers use it to connect the textbook cylinder to a concrete household object, including the classic six-inch by one-hundred-foot example that yields about one hundred forty-seven gallons. Expense, permit, and well-log products call the contract from scripts when a user logs a casing diameter and a standing level and the app must show gallons without shipping a hydrogeology engine.
Keep requests inside the published magnitude ceiling, pin the six-decimal gallons in tests, and you get a reproducible well volume for family notebooks, LMS plugins, and edge workers without standing up a borehole model of your own.
What you can do with it
Pump and recovery planning
Enter the casing inside diameter in inches and the standing water column in feet to see how many US gallons sit in the well before you size a pump or time a recovery test.
Shock chlorination dose
Convert a six-inch or eight-inch log into gallons so a bleach worksheet uses the water actually stored in the casing, not the total drilled depth.
FAQ
How does the well volume calculator compute gallons?
Send diameter in inches and depth in feet. Gallons equal π times (diameter / 2) squared times (depth × 12), divided by 231 cubic inches per US gallon.
What happens if diameter or depth is zero or negative?
A non-positive casing or water column does not define a stored volume, so the calculator will not invent a silent zero or a negative tank.
Which units should I enter?
Use inches for the casing inside diameter and feet for the standing water column. This landing does not convert mixed metric and imperial units for you.
Is depth the total well depth or the water column?
Use the standing water-column height — the wet height inside the casing — not the total drilled depth. The dry riser above the static level holds air, not gallons.
What does the well volume calculator cost?
It is free in your browser on this page.
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/life/well-volume \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"diameter":6,"depth":100}'const res = await fetch("https://api.kit.forhosting.com/life/well-volume", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"diameter": 6,
"depth": 100
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/life/well-volume",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"diameter": 6,
"depth": 100
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/life/well-volume", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"diameter":6,"depth":100}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"diameter":6,"depth":100}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/life/well-volume", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"diameter": 6,
"depth": 100
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "life.well_volume",
"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
Diameter and depth must be positive finite numbers; a zero or negative casing, or a zero or negative water column, is rejected as invalid_input rather than inventing an empty or negative tank.
How the well volume calculator turns diameter and depth into gallons
The water sitting in a cased well occupies a right circular cylinder whose radius is half the inside diameter of the casing and whose height is the standing water column, not the total drilled depth. This well volume calculator therefore asks for two everyday numbers: diameter in inches, because well casing is sold and logged as four-inch, six-inch, or eight-inch pipe, and depth in feet, because tapes, airline gauges, and e-lines report the water column in feet. The engine converts the water column to inches, multiplies π by the squared radius in inches by that height, and divides by two hundred thirty-one — the exact number of cubic inches in one US liquid gallon. A six-inch well with one hundred feet of standing water holds about one hundred forty-six point eight eight gallons; an eight-inch well with fifty feet of water holds about one hundred thirty point five six gallons. You send required fields diameter and depth as JSON numbers or numeric strings. Aliases D, diam, well_diameter, casing_diameter, and diameter_in map to diameter; water_depth, water_column, standing_water, h, and depth_ft map to depth. The response echoes both inputs after stable six-decimal rounding, plus gallons, cubic_feet, a method tag, and a formula string you can print next to a well log. There is no aquifer model, no live water-level feed, and no date-dependent shortcut: the engine either builds two finite positive figures inside the supported numeric range or rejects the input with invalid_input. That honesty is the point of a household well volume calculator.
Input contract, units, and the required positive-number checks
Optional leading plus signs and scientific notation on numeric strings are allowed when they parse as finite decimals; embedded spaces, hex prefixes, and non-numeric tokens are rejected with a message that names the field, so a bad cell does not become a wrong tank fill. After validation the engine applies the school identity: cubic inches equal π times radius squared times height in inches, gallons equal that volume divided by two hundred thirty-one, and cubic feet equal the same volume divided by one thousand seven hundred twenty-eight. Diameter and depth must be strictly positive. Do not send total well depth when you mean the water column: the dry riser above the static level holds air, not gallons you can pump or chlorinate. The preferred fields are diameter for the casing inside diameter in inches and depth for the standing water column in feet, but the documented aliases are accepted so spreadsheets, query strings, and typed forms can reuse the same contract without renaming columns. A zero or negative casing does not define a cylinder of water, and a zero or negative water column does not define a stored volume, so both cases fail with invalid_input. That is the specified error path. Do not mix metres with inches on the same payload; convert first so both numbers share the published convention. Magnitude caps keep results finite on the Worker isolate. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline.
Where a well volume calculator belongs in daily work and software
On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the tier-A catalog and lets you move from a kitchen-table demo to an automated pipeline without changing the mathematical result. This endpoint does not add drawdown, recovery time, or gravel-pack porosity; it answers the standing cylindrical volume only.
Integration use cases
Deterministic fixtures for well-log apps
Generate reproducible gallons and cubic_feet fields for permit tools, CI assertions, and simple household well notebooks.