Hydroxide concentration from pOH calculator
Convert pOH straight into hydroxide concentration: a pOH of 7 gives 1 × 10⁻⁷ mol/L, the neutral point of pure water at 25 °C, and a pOH of 1 gives a tenth of a mole per litre. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Solution pOH
- 7
- Oh minus
- 0.0000001 mol/L
- Hydroxide ion mol l
- 0.0000001
pOH is the logarithmic scale for hydroxide ion activity in aqueous solutions. Once you know the pOH of a sample, the molar hydroxide ion concentration follows from a single base-ten power: ten raised to the negative of that pOH value. This capability takes one finite numeric pOH and returns the hydroxide concentration in moles per litre with a pure deterministic formula—no network calls, no temperature tables, and no random behaviour. Non-numeric pOH is rejected with a clear invalid input error so bad form fields never produce a silent wrong number.
What pOH means and how hydroxide concentration is defined
pOH is defined as the negative base-ten logarithm of the hydroxide ion activity. In dilute ideal solutions classroom chemistry treats it as the negative log of the molar hydroxide concentration, so rearranging gives hydroxide concentration equal to ten to the power of minus pOH. At twenty-five degrees Celsius pure water has pOH seven and a hydroxide concentration of one times ten to the minus seven moles per litre, matching the familiar neutral point.
Basic solutions have lower pOH and higher hydroxide concentration; acidic solutions reverse that picture. This calculator does not require you to enter pH or Kw: if you already measured or calculated pOH, the hydroxide concentration is a direct power. Use this tool when the search question is specifically hydroxide concentration from pOH rather than a full pH-to-pOH conversion package.
How to read the result and its formula
The unit field is always mol per litre, and the formula string restates open bracket OH close bracket equals ten to the power of minus pOH. For a neutral classroom example with poh seven you get a hydroxide concentration of one times ten to the minus seven. For a strong base example with poh one you get a concentration of one tenth mole per litre.
For a more acidic-side pOH of fourteen the concentration is one times ten to the minus fourteen. Prefer the structured numbers for pipelines and auto-graders; use formula when a human-readable caption is enough for a report or slide.
What you can do with it
Lab notebook and LIMS helpers
Bench apps convert recorded pOH into molar hydroxide ion concentration fields for sample records without re-deriving the power formula in every language.
FAQ
What happens if pOH is not a number?
Non-numeric pOH values are rejected and not charged.
Is the hydroxide concentration from pOH calculator free?
The browser tool runs free on your device.
Does this convert pH to pOH?
No. This product starts from pOH and returns only the hydroxide concentration. For pH → pOH and both ion concentrations, use a dedicated pH to pOH calculator.
Does a lower pOH mean more hydroxide?
Yes. Basic solutions have a lower pOH and more hydroxide ions, and acidic solutions the reverse. Because the conversion is a power of ten, a small change in pOH means a large change in concentration.
Does the result change with temperature?
No. The conversion is a straight power of ten and does not adjust the water constant for other temperatures. The familiar neutral point at a pOH of 7 belongs to pure water at 25 °C.
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/hydroxide-from-poh \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"poh":7}'const res = await fetch("https://api.kit.forhosting.com/chem/hydroxide-from-poh", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"poh": 7
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/hydroxide-from-poh",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"poh": 7
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/hydroxide-from-poh", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"poh":7}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"poh":7}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/hydroxide-from-poh", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"poh": 7
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.hydroxide_from_poh",
"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
Students checking lab homework, tutors building auto-graded drills, and pipelines that already store pOH can pin the JSON in tests.
What pOH means and how hydroxide concentration is defined
Send the required field poh as a JSON number or a numeric string; aliases pOH and p_oh are accepted. Missing fields, empty strings, and non-numeric text such as words or mixed tokens fail with invalid_input and are not charged. Identical numeric inputs always produce identical JSON because the path is pure arithmetic with no wall clock, no seed, and no remote chemistry database.
Reading the response fields and the concentration formula
On success the response echoes the parsed poh, reports oh_minus as the hydroxide ion concentration in moles per litre, and repeats the same value under the longer key hydroxide_ion_mol_l so SDK clients can pick either naming style. The method label is always hydroxide_from_poh so downstream code can branch without sniffing shapes. Validation failures for non-numeric pOH never invent a concentration—they surface invalid_input with a message that names the field and the expectation.
API usage, pricing, classroom workflows, and practical limits
Call the free in-browser hydroxide concentration from pOH calculator for homework checks, lecture demos, and quick lab-bench verification without installing spreadsheet macros or a local chemistry package. The model does not adjust Kw for other temperatures, does not solve buffer equilibria, and does not accept pH or ion concentrations as primary inputs—those are different search intents and different products. Send a JSON body with the required finite number poh. Use the prepaid API when a tutoring platform, LMS auto-grader, curriculum generator, or lab notebook service 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 pH-to-pOH conversion when you start from pH, or with dilution and molarity tools when the next step is solution prep. Authors shipping SDKs can map oh_minus directly into UI tables that show pOH beside molar hydroxide concentration—the same layout students write by hand when they convert logarithmic scales on paper.
Integration use cases
Homework and exam verification
Students enter a given pOH and check [OH−] against answer keys; non-numeric pOH returns a clear invalid_input error instead of a silent wrong number.
Tutoring and curriculum generators
Lesson builders produce worked pOH → [OH−] examples with structured JSON for flashcards, step sheets, and auto-graded drills.
Technical questions
How do I calculate hydroxide concentration from pOH?
Send JSON with poh set to a finite number (for example poh: 7). The response includes oh_minus and hydroxide_ion_mol_l equal to 10^(−pOH) in mol/L.
What formula does this calculator use?
It uses [OH−] = 10^(−pOH). The formula string is always returned in the JSON response for display and auditing.