Combined gas law final volume calculator
See what volume a gas takes when pressure and temperature change together: 5 litres at 2 atm and 250 K become 20 litres at 1 atm and 500 K. Enter the starting state, the new pressure and the new kelvin temperature. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Initial pressure
- 1
- Initial gas volume
- 2
- Initial absolute temperature
- 300
- Final pressure
- 2
- Final absolute temperature
- 300
- V2
- 1
- Precision
- 10
This combined gas law final volume calculator finds the final gas volume when both pressure and temperature change for a fixed amount of ideal gas. You supply the initial pressure P1, initial volume V1, initial absolute temperature T1, the new pressure P2, and the new absolute temperature T2; the engine returns the final volume V2 from the classical identity P1 times V1 over T1 equals P2 times V2 over T2, which rearranges to V2 equals P1 times V1 times T2 over P2 times T1. That identity is the combined gas law: Boyle and Charles in one proportion when the amount of gas is fixed. Worked checks include P1 equals one, V1 equals two, T1 equals three hundred, P2 equals two, T2 equals three hundred yielding V2 equals one, and P1 equals two, V1 equals five, T1 equals two hundred fifty, P2 equals one, T2 equals five hundred yielding V2 equals twenty. Temperatures must be absolute (typically Kelvin); zero P2 or zero T1 is rejected because the rearrange divides by those values. The path is pure finite arithmetic with no network calls, no sampling, and no date-dependent shortcuts.
What the combined gas law final-volume rearrange computes and returns
The combined gas law states that, for a fixed amount of ideal gas, the product of pressure and volume divided by absolute temperature is the same in any two states. In symbols P1 V1 over T1 equals P2 V2 over T2. Solving exclusively for the unknown final volume gives the closed form V2 equals P1 times V1 times T2 divided by P2 times T1.
This calculator is dedicated to that single rearrange: it does not solve for an arbitrary missing variable among six state values, does not convert between Celsius and Kelvin for you, and does not apply Charles or Boyle alone when you only change temperature or only change pressure. Absolute temperatures must already be on a consistent absolute scale, and pressures and volumes must share consistent unit families across the two states.
Where combined-gas final volume fits in study, labs, and software
Students meet the combined gas law when a textbook moves from Boyle and Charles separately to problems where both pressure and temperature change between two states of a closed sample, when a lab asks how much a piston moves after a simultaneous heat and pressure change, or when a problem couples absolute temperature ramps to new external pressure under fixed moles. Teachers can pre-generate answer keys for modest pressures, volumes, and absolute temperatures without trusting opaque calculator apps that silently mix Celsius with Kelvin or drop the fixed-amount assumption.
Developers call the same contract from scripts to seed deterministic test vectors for gas-law tutors, to normalize user-entered P1, V1, T1, P2, and T2 before a multi-step ideal-gas demo, or to satisfy programming-challenge statements that demand V2 rather than a hand-waved sketch. Contest practice often needs a fast, offline source of final-volume answers so solutions can be checked without graphing calculators under time pressure. Product and education tools use the rearrange when a learner types the five known state quantities and the UI must show the scaled final volume.
What you can do with it
Homework and lab volume checks
Compute final volume from P1, V1, T1, P2, and T2 using V2 = P1·V1·T2/(P2·T1) before writing lab conclusions or multi-step gas-law follow-ups.
Tutoring and education software
Normalize user-entered pressures, volume, and absolute temperatures into final volume for interactive combined gas law lessons.
FAQ
What does the combined gas law final volume calculator cost?
It is free in your browser on this page.
How is V2 defined?
From P1·V1/T1 = P2·V2/T2 with fixed amount of gas, so V2 = P1·V1·T2/(P2·T1) using absolute temperatures.
Must temperatures be in Kelvin?
They must be on an absolute temperature scale (Kelvin or Rankine). Do not pass Celsius or Fahrenheit without converting first.
Does this tool change the amount of gas?
No. The combined gas law here assumes fixed moles of ideal gas; only pressure, volume, and absolute temperature link the two states.
What happens if the new pressure or the starting temperature is zero?
The calculator rejects the input, because the formula divides by both of them. Temperatures must also be absolute and above zero kelvin, and volumes cannot be negative.
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/combined-gas-final-volume \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"P1":1,"V1":2,"T1":300,"P2":2,"T2":300}'const res = await fetch("https://api.kit.forhosting.com/chem/combined-gas-final-volume", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"P1": 1,
"V1": 2,
"T1": 300,
"P2": 2,
"T2": 300
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/combined-gas-final-volume",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"P1": 1,
"V1": 2,
"T1": 300,
"P2": 2,
"T2": 300
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/combined-gas-final-volume", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"P1":1,"V1":2,"T1":300,"P2":2,"T2":300}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"P1":1,"V1":2,"T1":300,"P2":2,"T2":300}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/combined-gas-final-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
{
"P1": 1,
"V1": 2,
"T1": 300,
"P2": 2,
"T2": 300
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.combined_gas_final_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_value | 1000000000000000 |
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
What the combined gas law final-volume rearrange computes and returns
The response returns the normalized inputs P1, V1, T1, P2, and T2, the computed final volume V2, the precision used, a method tag combined_gas_law_final_volume, a short formula string, and a conditions reminder that the amount of gas is fixed, temperatures are absolute, and units are consistent. There is no approximate Monte Carlo path and no lookup table of compressibility factors: the engine either builds exact floating-point V2 inside the supported magnitude range or rejects the input with invalid_input. Rejected cases include missing required fields, non-finite values, magnitudes above the documented ceiling, negative volume, non-positive absolute temperatures, and any P2 or T1 that is zero or numerically zero, because those quantities appear in the denominator of the final-volume rearrange.
How P1, V1, T1, P2, and T2 are read and how V2 stays reproducible
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 clear message so a bad cell does not become a wrong final volume. Zero for V1 is valid and simply yields zero final volume when the other factors are finite, corresponding to an empty sample under the ideal proportion. Final temperature T2 must be positive and non-zero so the physical state remains well defined on an absolute scale. The preferred fields are P1 for initial pressure, V1 for initial volume, T1 for initial absolute temperature, P2 for final pressure, and T2 for final absolute temperature, but aliases p1, pressure1, and initial_pressure for P1, v1, volume1, and initial_volume for V1, t1, temperature1, and initial_temperature for T1, p2, pressure2, final_pressure, and new_pressure for P2, and t2, temperature2, final_temperature, and new_temperature for T2 are accepted so spreadsheets, query strings, and typed forms can reuse the same contract. The divisors P2 and T1 must be strictly non-zero: if either is at or below a tiny epsilon, the request fails with invalid_input because the combined-gas rearrange divides by P2 times T1. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for all numeric fields, defaulting to ten and capped at fifteen so JSON goldens stay stable. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing the combined gas formula yourself.
Where combined-gas final volume fits in study, labs, 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 KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the mathematical result. Pair it with Charles-only final volume, Avogadro moles, or STP volume tools when you need related chemistry steps, and with other parse endpoints when you are building a small lab of free, deterministic science helpers.
Integration use cases
Deterministic test fixtures
Generate reproducible V2 values for unit tests, property checks, and CI assertions on combined-gas tutors and homework checkers.
Technical questions
What happens if P2 or T1 is zero?
The input is rejected with invalid_input. Those fields are divisors in the final-volume rearrange, so zero is undefined.