Strong base pH calculator
0.1 mol/L sodium hydroxide gives pH 13: enter the base concentration and how many hydroxide ions each formula unit releases, and get the hydroxide and hydrogen ion concentrations, the pOH and the pH at 25 °C. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Concentration
- 0.1
- Hydroxide count
- 1
- Oh minus
- 0.1
- H plus
- 0
- Poh
- 1
- Ph
- 13
This strong base pH calculator returns the aqueous solution pH when you know the molar concentration of a strong base and how many hydroxide ions each formula unit releases. For a fully dissociating base B(OH)n, the hydroxide-ion concentration equals n times the base concentration C in moles per litre, pOH is the negative base-ten logarithm of that value, and pH equals fourteen minus pOH at twenty-five degrees Celsius where Kw is one times ten to the minus fourteen. Classroom checks you already know include zero point one molar sodium hydroxide with n equal to one yielding pH thirteen, and zero point zero five molar calcium hydroxide with n equal to two also yielding pH thirteen because both give zero point one molar hydroxide. Concentrations that push n times C above one mole per litre produce pH above fourteen, which is retained rather than clamped. The engine uses only finite deterministic arithmetic with no network calls, no sampling, and no date-dependent shortcuts.
What strong-base pH means
pH measures how acidic or basic an aqueous solution is on a logarithmic scale tied to hydrogen-ion activity. In the introductory strong-base model used in general chemistry, a base such as NaOH, KOH, or Ca(OH)2 that is strong dissociates completely, so every formula unit contributes a fixed number n of hydroxide ions and the equilibrium hydroxide-ion concentration is taken equal to n times the formal base concentration C in moles per litre.
The defining relations are then pOH equals negative log base ten of the hydroxide-ion concentration, and pH equals fourteen minus pOH when water autoionization is summarized by Kw equals one times ten to the minus fourteen at twenty-five degrees Celsius and activity corrections are neglected.
That approximation is the standard homework path for sodium hydroxide, potassium hydroxide, barium hydroxide, and similar fully dissociating bases at concentrations where the base contribution dominates, and it produces familiar integers such as pH thirteen for zero point one molar monohydroxide base and pH twelve for zero point zero one molar monohydroxide base.
Where strong-base pH fits in study, lab work, and software
Students meet pH equals fourteen plus log ten of n times C when a textbook introduces strong bases, when a homework problem gives molarity of NaOH or Ca(OH)2 and asks for pH, or when a contest problem expects an integer answer without a graphing calculator that silently applies weak-base quadratic formulas. Teachers can pre-generate answer keys for stock base dilutions and safety discussions without trusting opaque apps that confuse strong and weak bases or report pH seven for every dilute solution.
Lab technicians use the same definition when a protocol states a strong-base molarity and a quick pH estimate is needed before meter calibration or when planning how far a concentrate will sit above neutral. Developers call the same contract from scripts to seed deterministic test vectors for chemistry tutors, to normalize user-entered base concentrations before a lab notebook export, or to satisfy programming-challenge statements that demand pH rather than a hand-waved basicity rank.
What you can do with it
Homework and lab checks
Compute pH from C and n for strong bases such as NaOH and Ca(OH)2 before grading worksheets or preparing stock solutions.
Education and lab software
Normalize user-entered strong-base molarity and OH stoichiometry into pH for plotters, quizzes, and interactive lessons.
FAQ
What does the strong base pH calculator cost?
It is free in your browser on this page.
What happens if concentration is zero or negative?
Non-positive concentration makes [OH−] = n·C non-positive and the strong-base pH relation undefined or non-physical.
Does this tool handle weak bases or buffers?
No. It only models a strong base with [OH−] = n·C. Use a weak-base or buffer solver if you need Kb or Henderson–Hasselbalch.
How do I handle calcium hydroxide and other bases with two hydroxides?
Set the number of hydroxide ions per formula unit to 2. Then 0.05 mol/L calcium hydroxide gives 0.1 mol/L of hydroxide and pH 13, the same as 0.1 mol/L sodium hydroxide with one hydroxide.
Can the pH of a strong base go above 14?
Yes. When the concentration times the number of hydroxide ions exceeds 1 mol/L, the pH rises above 14. The calculator keeps that value instead of capping it, because it follows from the same formula.
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/ph-strong-base \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"concentration":0.1,"hydroxide_count":1}'const res = await fetch("https://api.kit.forhosting.com/chem/ph-strong-base", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"concentration": 0.1,
"hydroxide_count": 1
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/chem/ph-strong-base",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"concentration": 0.1,
"hydroxide_count": 1
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/chem/ph-strong-base", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"concentration":0.1,"hydroxide_count":1}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"concentration":0.1,"hydroxide_count":1}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/chem/ph-strong-base", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"concentration": 0.1,
"hydroxide_count": 1
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "chem.ph_strong_base",
"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 strong-base pH means and what the response contains
This calculator returns the input concentration, the hydroxide count, the implied hydroxide-ion concentration oh_minus equal to n times C, the implied hydrogen-ion concentration h_plus from Kw over oh_minus, the computed pOH and pH, the precision used, a method tag strong_base_ph, a short formula reminder, unit hints, and the Kw and pKw constants used. There is no Kb path for weak bases, no buffer equation, and no charge-balance solver that adds extra water autoionization beyond the fixed Kw link: the engine either evaluates fourteen plus log ten of n times C inside the supported numeric range or rejects the input with invalid_input. Rejected cases include a missing concentration or hydroxide count, non-finite values, magnitudes above the documented ceiling, and any concentration that is zero or negative because the logarithm is undefined or non-physical for non-positive hydroxide concentration.
How concentration and hydroxide count are read and how pH stays reproducible
Hydroxide count must also be finite and strictly positive. 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. When n times C is greater than one mole per litre, pH rises above fourteen and is retained rather than clamped. The preferred field is concentration for the base molarity in moles per litre, but aliases C, c, molarity, conc, mol_L, M, and base_concentration are accepted so spreadsheets, query strings, and typed forms can reuse the same contract. Concentration must be a finite positive number: zero or negative values fail with invalid_input and a message that names the field and explains that non-positive concentration makes n times C non-positive and the strong-base pH relation undefined or non-physical, so a bad cell does not become a silent NaN or infinity. The preferred field for stoichiometry is hydroxide_count, with aliases n, oh_count, oh_per_formula, stoichiometry, and hydroxide_ions; use one for monohydroxide bases such as NaOH and KOH, two for dihydroxide bases such as Ca(OH)2 and Ba(OH)2, and three when modeling a trihydroxide strong base in the introductory complete-dissociation idealization. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for concentration, hydroxide_count, oh_minus, h_plus, poh, and ph, 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 strong-base pH formula yourself.
Where strong-base pH fits in study, lab work, and software
Product and education tools use the endpoint when a learner types concentration and hydroxide count and the UI must show pH with a clear strong-base assumption. 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 molar concentration or dilution helpers when you need related solution quantities, with the strong-acid pH calculator when comparing conjugate strong pairs, and with other science endpoints when you are building a small lab of free, deterministic chemistry calculators for acid-base practice.
Integration use cases
Deterministic test fixtures
Generate reproducible strong-base pH values for unit tests, chemistry tutors, and CI assertions on pH = 14 + log10(n·C).
Technical questions
How is pH defined for a strong base?
For full dissociation, [OH−] equals n times the base concentration C in mol/L, pOH = −log₁₀([OH−]), and pH = 14 − pOH at 25 °C.
What is hydroxide_count (n)?
It is the number of OH− ions released per formula unit: 1 for NaOH or KOH, 2 for Ca(OH)2 or Ba(OH)2, and so on.