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Chemistry

pH and pOH Calculator

Convert hydrogen-ion concentration to pH, pOH and hydroxide concentration using an explicit pKw.

Explicit units and model assumptionsLocal calculations with worked examples
Chemistry workspace
Chemistry workspace

Check the units, concentration basis and assumptions before interpreting the result.

See the method

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Your chemistry result

Your result

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Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter hydrogen-ion concentration, pkw.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

pH = −log10([H+]); pOH = pKw − pH; [OH−] = 10^(−pOH). In dilute water near 25°C, pKw is approximately 14.

A WORKED EXAMPLE

Using hydrogen-ion concentration = 0.0001 mol/L, pkw = 14, the result is 4 pH. Change these example inputs to match your task; use the method above to check each step.

Understanding your result

No. That is a familiar dilute-water range, not an absolute mathematical limit. Concentrated solutions need activity corrections, which this model does not apply.

What to keep in mind

Concentrations approximate activities in dilute solutions. This is not a measured pH and does not infer [H+] from an undissociated acid concentration. Educational calculation only; use validated procedures for laboratory work.

Reference: OpenStax Chemistry 2e — chemical quantities and models

Common questions

Must every pH fall between 0 and 14?

No. That is a familiar dilute-water range, not an absolute mathematical limit. Concentrated solutions need activity corrections, which this model does not apply.

Are my inputs uploaded?

No. This calculation runs in your browser without an account or an external API.

Methodology maintained by ClarityKit. How these tools are built and checked.