Standard cell potential calculator
Copper at +0.34 V as cathode and zinc at −0.76 V as anode give a standard cell potential of +1.10 V. Enter both reduction potentials to get E° of the cell, the anode's oxidation potential and whether the cell is spontaneous. Free in your browser.
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- Your data stays on your device
Run — free
Worked example
- Cathode
- 0.34
- Anode
- -0.76
- E cathode
- 0.34 V
- E anode
- -0.76
- E ox anode
- 0.76
- E cell
- 1.1
The standard cell potential is the voltage a galvanic cell would deliver when every species is in its standard state: unit activity, one bar pressure for pure gases, and typically twenty-five degrees Celsius. Textbooks build that number from tabulated standard reduction potentials by placing the more positive half-cell as the cathode (reduction) and the less positive half-cell as the anode (oxidation). This capability implements that classroom formula deterministically: E°_cell equals E°_cathode minus E°_anode, with both inputs treated as reduction potentials in volts. You supply the two numbers; the engine returns the cell potential, the anode oxidation potential as the sign-flipped anode reduction value, a spontaneous flag when the result is positive, and fixed formula labels for UI and grading tools. Non-numeric potentials fail with a clear invalid input error so homework bots and APIs never invent a voltage from garbage.
How standard cell potential is defined from half-cells
Every electrochemical cell couples a reduction half-reaction with an oxidation half-reaction. Tables of standard reduction potentials list each couple against the standard hydrogen electrode on a single voltage scale. For a spontaneous galvanic cell under standard conditions, reduction occurs at the cathode and oxidation at the anode, so the standard cell potential is E°_cathode minus E°_anode when both values are taken from those reduction tables.
Equivalently you may add the cathode reduction potential to the anode oxidation potential, remembering that the oxidation potential is simply the negative of the tabulated reduction potential for that couple. A positive E°_cell means the cell reaction as written is spontaneous under standard conditions; a negative value means the reverse direction is favored and you have either swapped electrodes or described an electrolytic cell.
Classic copper-zinc Daniell-cell numbers illustrate the arithmetic: copper reduction near plus zero point three four volts as cathode and zinc reduction near minus zero point seven six volts as anode yield about plus one point one zero volts. Always feed reduction potentials for both electrodes; never mix an oxidation potential into the anode field without flipping the sign first.
FAQ
What happens if a potential is non-numeric?
Both cathode and anode must be finite numbers (or numeric strings); text, NaN, Infinity, and objects are rejected and not charged.
Are the inputs reduction or oxidation potentials?
Both fields expect standard reduction potentials from the usual half-cell tables. The engine computes the anode oxidation potential internally as the negative of the anode reduction value.
Is the standard cell potential calculator free?
The browser tool runs free on your device.
How is this different from the Nernst equation calculator?
This tool returns E° from two half-cell potentials. The Nernst calculator adjusts a known E° for non-standard conditions using n, Q, and optional temperature. Different search intent, different inputs.
What does a negative standard cell potential mean?
The reaction as written is not spontaneous under standard conditions and the reverse direction is favored. Usually the electrodes are swapped, or you are describing an electrolytic cell; the result is then marked as not spontaneous.
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/standard-cell-potential \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"cathode":0.34,"anode":-0.76}'const res = await fetch("https://api.kit.forhosting.com/chem/standard-cell-potential", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"cathode": 0.34,
"anode": -0.76
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/standard-cell-potential",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"cathode": 0.34,
"anode": -0.76
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/standard-cell-potential", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"cathode":0.34,"anode":-0.76}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"cathode":0.34,"anode":-0.76}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/standard-cell-potential", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"cathode": 0.34,
"anode": -0.76
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.standard_cell_potential",
"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
How standard cell potential is defined from half-cells
The engine does not assign which metal is cathode or anode from chemistry names—that assignment is yours before you call the API. Identical numeric inputs always produce identical JSON because the path is pure arithmetic with no network, no random seed, and no wall clock.
Reading the response fields and handling invalid input
Numeric strings such as scientific notation are accepted when they parse to a finite number. On success the response echoes cathode and anode as finite numbers, repeats them as e_cathode and e_anode for consistent SDK field names, and reports e_ox_anode as the negated anode reduction potential. The spontaneous boolean is true only when e_cell is strictly greater than zero, matching the usual first-year rule that a positive standard cell potential drives a galvanic cell forward under standard conditions. Zero is treated as not spontaneous in that boolean sense even though equilibrium thermodynamics is a separate topic. The formula string is always E°_cell equals E°_cathode minus E°_anode, and formula_alt restates the reduction-plus-oxidation form for lecture slides. The method label is always standard_cell_potential so downstream code can branch without sniffing shapes. Missing cathode or anode, empty strings, boolean flags, objects, arrays, NaN, Infinity, and non-numeric text all fail with invalid_input and are not charged after the engine rejects the request. Pair this endpoint with a Nernst calculator when the next homework step needs non-standard E from E°, n, and Q; this product stops at the standard value so search intent and grading rubrics stay clean.
API usage, pricing, classroom workflows, and practical limits
Call the free in-browser standard cell potential calculator for homework checks, lecture demos, and quick verification of tabulated half-cell arithmetic without installing a chemistry package. Do not expect species lookup: if you only know half-reactions by formula, look up E° values first, then pass the numbers here. Large positive or negative voltages are allowed as long as they remain finite; physical reasonableness is left to the caller and the laboratory context. Send a JSON body with the required finite numbers cathode and anode, using documented aliases such as E_cathode or anode_potential if your client code already uses those names. Use the prepaid API when a tutoring platform, lab notebook assistant, exam sandbox, or curriculum generator needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance. Authors shipping SDKs can map e_cell and spontaneous directly into UI tables next to electrode labels, and they can feed e_cell into a Nernst equation tool as the standard potential when concentrations leave the standard state.
Integration use cases
Homework and exam verification
Students plug cathode and anode standard reduction potentials into the calculator, confirm E°_cell, and receive a clear invalid_input error when a non-numeric value is submitted by mistake.
Tutoring and curriculum generators
Lesson builders produce worked galvanic-cell examples with structured JSON for flashcards, step sheets, and auto-graded drills without embedding a full electrochemistry stack.
Lab notebook and pipeline checks
Scripts that already store half-cell table values call a stable prepaid endpoint to compute E°_cell before chaining into Nernst or free-energy steps.
Technical questions
How do I calculate standard cell potential from cathode and anode?
Send JSON with cathode and anode set to standard reduction potentials in volts (for example cathode: 0.34, anode: -0.76). The response includes e_cell equal to cathode minus anode.