Gas volume from moles calculator
One mole at 101325 Pa and 273.15 K takes up 0.022413969545 m³, straight from V = nRT/P. Give the moles, pressure and absolute temperature, keep the SI gas constant or use 0.082057 for litres, and see every substitution. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- N
- 1
- Power (W)
- 101,325
- Absolute temperature
- 273.15
- Moles
- 1
- Pressure
- 101,325
- Creativity
- 273.15
- Temperature kelvin
- 273.15
A gas volume from moles calculator turns the amount of gas, the pressure, and the absolute temperature into the ideal-gas volume you expect from the rearranged law V equals n R T over P. Enter moles n, pressure P, and temperature T in kelvin; optionally set the gas constant R to match your pressure–volume units, or keep the SI default so pascals and cubic metres stay consistent. Classroom stoichiometry, process estimates at fixed composition, and coding kata expected values all need that same V equals nRT over P path without opening a full multi-unknown equation-of-state solver.
What V = nRT/P means for an ideal gas
When you already know how many moles of gas you have, the pressure of the vessel or atmosphere, and the temperature on the kelvin scale, the single unknown of interest is often the volume the sample occupies. Rearrangement isolates V as V equals n R T divided by P. At higher pressure the same amount of gas is squeezed into a smaller volume; at higher temperature or more moles the volume grows linearly if pressure is held fixed.
Temperature must be absolute: zero or negative kelvin is not a valid thermodynamic state for this model, and the calculator rejects those inputs rather than inventing a volume. Pressure must be strictly positive: zero or negative pressure would make the division undefined or non-physical, and that rejection is part of the contract of this landing. Chemistry worksheets that work in litres and atmospheres should pass approximately zero point zero eight two zero five seven for R so that V comes back in litres.
Teachers and automated graders care about the pressure-rejection path as much as the happy path: a student who sets P to zero has left the domain of the formula, and printing infinity would hide that mistake. The check path recomputes n R T over P with the same fixed twelve-decimal rounding used for published fields, so a successful response always ships with steps you can assert in tests or worksheets.
Practical tips, limits, and related searches
Keep inputs inside the published absolute range so the product n R T over P cannot overflow into a non-finite volume that the solver must reject. Prefer sending numbers rather than pre-formatted strings when you control the client; string numbers are accepted only when they match a strict finite numeric pattern.
Match R to your pressure and volume units before comparing textbook answers: one mole at about one hundred one thousand three hundred twenty-five pascals and two hundred seventy-three point one five kelvin with the SI R yields roughly zero point zero two two four cubic metres, while the same state with R about zero point zero eight two zero five seven and P equals one atmosphere yields about twenty-two point four litres.
Prefer this capability when moles, pressure, and temperature are known and volume is the only unknown; if a different variable is missing, use a full ideal-gas law solver instead. Round-trip checks are easy: recompute n times R times T divided by P by hand and confirm it equals the published volume within the same twelve-decimal rounding, and confirm that doubling moles at fixed P and T doubles volume.
What you can do with it
Lab and process volume estimates
Engineers estimate the volume a known mole count of ideal gas occupies at measured pressure and bath temperature before sizing vessels or syringes.
FAQ
How do you calculate gas volume from moles?
For an ideal gas use V = nRT / P with n in moles, T in kelvin, P and R in consistent units. This tool performs that rearrange and returns volume with step-by-step substitution.
What happens when pressure is zero or negative?
The formula divides by pressure, so zero or negative P is invalid.
Which gas constant R should I use?
Default is 8.314462618 J/(mol·K) for SI (Pa and m³). For litre–atmosphere problems pass about 0.082057 L·atm/(mol·K) so volume is in litres.
Must temperature be in kelvin?
Yes. Absolute temperature in kelvin is required. Convert from Celsius first (T_K = t_C + 273.15); non-positive kelvin is rejected.
Is the gas volume from moles calculator free?
The browser tool is free and runs locally.
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/chem/gas-volume-from-moles \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"n":1,"p":101325,"t":273.15}'const res = await fetch("https://api.kit.forhosting.com/chem/gas-volume-from-moles", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"n": 1,
"p": 101325,
"t": 273.15
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/gas-volume-from-moles",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"n": 1,
"p": 101325,
"t": 273.15
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/gas-volume-from-moles", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"n":1,"p":101325,"t":273.15}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"n":1,"p":101325,"t":273.15}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/gas-volume-from-moles", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"n": 1,
"p": 101325,
"t": 273.15
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.gas_volume_from_moles",
"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
The tool returns the computed volume, dual-named fields for pressure and moles, product checks for P·V and n·R·T, a readable equation string, and ordered substitution steps so homework checks, lab write-ups, and pipeline tests all see the same deterministic JSON. When pressure is zero or negative the quotient is undefined or non-physical, so the API returns invalid_input instead of infinity or a silent nonsense volume.
What V = nRT/P means for an ideal gas
The ideal gas law states that pressure times volume equals the amount of substance times the gas constant times absolute temperature: P V equals n R T. The gas constant R is not optional in the physics—it carries the unit system—but it is optional in the request body because a default SI value of eight point three one four four six two six one eight joules per mole per kelvin is supplied for Pa·m³ problems.
How to call the API and what comes back
Moles n must be strictly positive; pressure p must be strictly positive—values at or below one times ten to the minus fifteen are treated as non-positive and rejected with a message that zero or negative pressure is not valid for V equals nRT over P; temperature t must be strictly positive in kelvin; R must be positive when provided. Send a JSON body with three required finite numbers: n (aliases moles, amount, mol), p (aliases pressure, P), and t (aliases temperature, T, temp, kelvin). Optionally include r (aliases R, gas_constant, gasConstant); when omitted the SI default is used. Absolute values must stay within the published limit of one trillion so intermediate products remain finite in IEEE double precision on the Worker and in the browser. On success the response echoes rounded n, p, t, and r under both short and long names, sets v and volume to the computed volume, formula to the string V equals nRT over P, rearrange to a dotted product form, equation to a P·V equals n·R·T identity check with substituted numbers, product_nrt and product_pv to the two sides of the ideal-gas product after rounding, message to a short English summary, and steps to an ordered array of substitution lines. Failed validation—missing fields, non-finite numbers, values outside absolute limits, non-positive moles, zero or negative pressure, non-positive temperature, or non-positive R—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, limits, and related searches
When teaching, pair examples: a standard molar volume style SI case; a litre–atmosphere classroom case with explicit R; and a deliberate p equals zero case that demonstrates the hard invalid_input path protecting division by zero. This landing targets people searching for a gas volume from moles calculator, ideal gas volume from n P T, or V equals nRT over P online; it is not a multi-unknown ideal-gas rearrange that also solves for P, n, or T, not an Avogadro mole-ratio tool that scales volume when only n changes at fixed T and P, and not a real-gas compressibility calculator. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately set pressure to zero.
Integration use cases
Homework checks for V = nRT/P
Students enter textbook moles, pressure, temperature, and optional R, then compare hand-written volume and product sides against a deterministic JSON result before submitting.
Unit tests for ideal-gas helpers
Generate known-good volume cases plus deliberate zero-pressure rejections for coding kata expected values and CI fixtures.