Kp from Kc calculator
Switch an equilibrium constant from concentrations to pressures: a Kc of 0.5 at 298.15 K with one extra mole of gas, a Δn of 1, becomes a Kp of 12.2327158495, using an R·T of 24.465431699. Free in your browser.
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Worked example
- Concentration-based equilibrium constant Kc
- 0.5
- Creativity
- 298.15
- Delta n
- 1
- Kp
- 12.2327158495
- Kp
- 12.2327158495
- Kc
- 0.5
- Resistance (Ω)
- 0.08205746
Heterogeneous and homogeneous gas-phase equilibria are often tabulated with a concentration equilibrium constant Kc, while process engineers and many textbook chapters prefer the pressure form Kp. Under the ideal-gas assumption the two constants are linked by a compact identity: Kp equals Kc times the quantity R times absolute temperature raised to the power of the change in moles of gas between products and reactants. This capability evaluates that conversion deterministically. You supply Kc, temperature in kelvin, and Δn; optionally override the gas constant when your pressure unit is not atmospheres. Zero or negative temperature fails with invalid input so non-physical kelvin values never become a silent wrong answer.
The Kp–Kc relation and how to choose Δn, T, and R
Start from the definitions of Kc and Kp written with partial pressures and molar concentrations for the gaseous species that appear in the balanced equation. Optional r defaults to zero point zero eight two zero five seven four six litre atmospheres per mole per kelvin, the textbook constant that keeps Kp in atmospheres when concentrations behind Kc are in moles per litre. If you work with bar, pass a matching R such as zero point zero eight three one four four six two six so the factor stays coherent.
Δn may be negative when fewer gas moles form, zero when the gas count does not change so that Kp equals Kc, or positive when the reaction produces more gas.
What you can do with it
Homework and exam verification
Students enter Kc, T, and Δn, compare returned Kp and the (RT)^Δn factor with hand work, and get a clear error when temperature is zero or negative.
FAQ
How do I convert Kc to Kp with this calculator?
The response includes kp equal to Kc times (R times T) raised to Δn.
What happens if temperature is zero or negative?
Absolute temperature must be positive kelvin so (R T)^Δn is defined and physical; zero and negative values are rejected and not charged.
Which gas constant R should I use?
Default R is 0.08205746 L·atm/(mol·K) for Kp in atm with mol/L concentrations. For bar, pass r around 0.083144626 and keep units coherent.
What if Δn is zero?
The factor (R T)^Δn is exactly 1, so Kp equals Kc. That covers reactions with no net change in gas moles.
Is the Kp from Kc calculator free?
The browser tool runs free on your device.
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/kp-kc-conversion \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"kc":0.5,"temperature":298.15,"delta_n":1}'const res = await fetch("https://api.kit.forhosting.com/chem/kp-kc-conversion", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"kc": 0.5,
"temperature": 298.15,
"delta_n": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/kp-kc-conversion",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"kc": 0.5,
"temperature": 298.15,
"delta_n": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/kp-kc-conversion", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"kc":0.5,"temperature":298.15,"delta_n":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"kc":0.5,"temperature":298.15,"delta_n":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/kp-kc-conversion", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"kc": 0.5,
"temperature": 298.15,
"delta_n": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.kp_kc_conversion",
"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
The response returns Kp, the intermediate factor (R T) to the Δn, the product R T, and the normalized inputs so students and pipelines can audit every step.
The Kp–Kc relation and how to choose Δn, T, and R
Substituting the ideal-gas link between partial pressure and concentration yields the working identity Kp equals Kc times open parenthesis R times T close parenthesis raised to Δn, where Δn is n_gas of products minus n_gas of reactants, R is the molar gas constant, and T is absolute temperature in kelvin. Send three required numbers: kc for the concentration equilibrium constant, temperature as a strictly positive kelvin value, and delta_n for that stoichiometric gas-mole difference. Identical inputs always produce identical JSON because the path is pure arithmetic with no random seed and no wall clock.
Reading Kp, the factor (R T)^Δn, and echoed inputs
The intermediate rt equals R times T, and factor equals open parenthesis R T close parenthesis to the power Δn so students can check the conversion multiplier separately from Kc. Use kp alone when a spreadsheet or gradebook needs a single number; use factor and rt when a lab report must show how temperature and gas-mole change shift the constant from concentration to pressure form. The engine never converts units of Kc itself; you remain responsible for feeding a Kc whose concentration units match the R you chose. On success the response includes kp and the alias Kp—both equal to the computed pressure equilibrium constant—plus kc and Kc echoing the concentration constant you supplied after alias resolution. Echoed fields temperature, delta_n, and r show the normalized numbers actually used, including the default gas constant when you omitted r. When Δn is zero the factor is exactly one and Kp equals Kc without invoking a noisy power evaluation. formula restates the identity as a short string, and method is always kp_from_kc so downstream code can branch without sniffing shapes. Missing required fields, non-finite numbers, negative Kc, and zero or negative temperature all fail with invalid_input and are not charged after the engine rejects the request.
API usage, pricing, classroom workflows, and practical limits
Call the free in-browser Kp from Kc conversion calculator for homework checks, lecture demos, and quick conversion of tabulated concentration constants into pressure form without installing a thermochemistry package. Send a JSON body with required fields kc, temperature, and delta_n; documented aliases such as Kc, K_c, equilibrium_constant, t, T, temp, delta_n_gas, dn, and n_gas are accepted when the SDK lists them. Use the prepaid API when a tutoring platform, LIMS integration, process-safety worksheet, or curriculum generator needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Magnitudes are bounded for Worker isolate safety while still covering ordinary classroom and industrial teaching examples. Pair this endpoint with a mass-action equilibrium constant calculator when the previous step is building Kc from concentrations, or with partial-pressure helpers when the next step is Dalton compositions at a given total pressure. Authors shipping SDKs can map kp, factor, and delta_n directly into UI tables that mirror the worked steps students write on paper when they convert Kc to Kp by hand.
Integration use cases
Curriculum and tutoring platforms
Lesson builders convert tabulated concentration constants into pressure form with structured JSON for auto-graded drills without embedding a full thermo stack.
Lightweight process and LIMS pipelines
Scripts that need a stable Kp from a known Kc call a prepaid endpoint instead of reimplementing the (RT)^Δn factor in every language.