Electric charge calculator
A steady 2 A flowing for 5 seconds moves 10 coulombs. Enter any two of charge, current and time and the calculator finds the third, refusing negative durations and any division by zero. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Current
- 2
- Time
- 5
- Charge
- 10
- Solved
- charge
Electric charge, current and time are linked by the elementary identity Q equals I times t. Given a steady current in amperes and a duration in seconds you recover the transferred charge in coulombs; given charge and time you recover current; given charge and current you recover how long the flow lasted.
What charge, current and time mean and which two to send
Electric charge Q measures how much electricity has been transferred, in coulombs. Current I is the rate of charge flow in amperes, equal to one coulomb per second under a constant-current model. Time t is the duration of that flow in seconds and must be non-negative because a duration cannot go backward in this product contract.
For a constant current the three quantities obey Q equals I times t with no integration step. Providing none, only one, or all three of the quantities fails with invalid input because the product would either be underdetermined or over-constrained. Convert milliamps, hours or milliamp-hours yourself before calling if your datasheet uses those units.
Formulas, solved field, negative time and division by zero
When current and time are known, the engine multiplies them to obtain charge and labels solved as charge with formula Q equals I times t. When charge and time are known, it divides charge by time to obtain current, labels solved as current and uses formula I equals Q over t. When charge and current are known, it divides charge by current to obtain time, labels solved as time and uses formula t equals Q over I.
Zero charge with a non-zero divisor is valid and yields zero for the unknown. Missing input objects, non-finite numbers and out-of-range magnitudes also fail with invalid input and are not charged.
What you can do with it
Constant-current charge and battery drills
Engineers and students enter known current and duration to recover transferred charge in coulombs, or known charge and current to recover how long a constant-current step must run.
Electrolysis and process timing estimates
Lab tools convert any two of charge, plating current and process time into the third quantity for simple constant-current process sheets.
FAQ
What happens if time is negative?
Duration must be non-negative; negative time is rejected whether you supply it or whether solving t = Q / I would produce a negative result.
Can I solve for current or time instead of charge?
Yes. Provide exactly two of charge, current and time and omit the unknown. The engine returns all three values, the field name it solved, and the formula used.
Is the charge calculator free?
The browser tool runs free on your device.
Which units should I use?
SI base units only: charge in coulombs (C), current in amperes (A), time in seconds (s). Convert mA, hours or mAh yourself before calling.
What happens if I enter all three values?
The calculation is refused. Give exactly two of the three and leave the unknown empty: with only one value there is nothing to solve, and with all three the values could contradict each other.
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/elec/charge-current-time \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"charge":10,"Q":1}'const res = await fetch("https://api.kit.forhosting.com/elec/charge-current-time", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"charge": 10,
"Q": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/elec/charge-current-time",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"charge": 10,
"Q": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/elec/charge-current-time", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"charge":10,"Q":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"charge":10,"Q":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/elec/charge-current-time", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"charge": 10,
"Q": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "elec.charge_current_time",
"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
This capability performs that solve deterministically from a JSON body, rejects incomplete or over-specified inputs, forbids negative time, and raises a clear invalid input error on division by zero so homework tools, battery estimators and lab pipelines never return infinity or NaN.
What charge, current and time mean and which two to send
Send exactly two of the three fields charge, current and time as finite JSON numbers or numeric strings; leave the unknown field out entirely so the engine knows which quantity to solve. Aliases such as Q, q and coulombs for charge, I, amps, amperes and A for current, and t, seconds and duration for time are accepted when you prefer textbook symbols. Magnitudes must stay within the published finite bounds so Worker isolates stay stable. Identical inputs always produce identical JSON because the path is pure arithmetic with no network, no random seed and no wall clock.
Formulas, solved field, negative time and division by zero
The method field is always q_equals_i_times_t so downstream code can branch without sniffing shapes. Negative time is never allowed: if you send a negative duration, or if solving t equals Q over I would produce a negative duration because charge and current have opposite signs under your convention, the request fails with invalid input and a message that names the negative time rule. Division by zero is also forbidden: if you ask for current while time is zero, or for time while current is zero, the request fails with invalid input and a message that names the zero divisor.
API usage, pricing, batteries, education and practical limits
Call the free in-browser charge calculator for quick coulomb checks, constant-current charge estimates, electrolysis homework and lab exercises without installing a spreadsheet. Authors shipping SDKs can map the solved and formula fields directly into UI copy that highlights which quantity was computed and which identity was used, matching what students write by hand when they rearrange Q equals I t on a worksheet. Send a JSON body with exactly two of charge, current and time. Use the prepaid API when a battery tooling service, IoT firmware test harness, physics tutoring platform or classroom grading pipeline needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Pair this endpoint with unit converters when inputs arrive in milliamps, hours or amp-hours, and with power calculators when the next unknown is watts rather than charge. This product does not integrate a time-varying current waveform, model capacitor voltage as Q equals C times V, or apply Coulomb force between point charges; those are distinct SEO intents covered by other tools.
Integration use cases
Physics homework and lab grading
Courses pin deterministic JSON fixtures for Q=I·t rearrangements, including intentional negative-time and division-by-zero cases that must fail with invalid_input.
Technical questions
How do I calculate electric charge with this calculator?
Send JSON with current in amperes and time in seconds (for example current: 2, time: 5). The response returns charge in coulombs via Q = I · t, plus the full triple and a solved label.