pH Calculator
Convert hydrogen ion concentration into pH and pOH, with the hydroxide concentration alongside.
Each pH step is a factor of ten
pH 4 is not slightly more acidic than pH 5 — it is ten times more. Stomach acid at pH 2 is a hundred thousand times more acidic than pure water. The logarithmic scale exists because hydrogen ion concentrations in real solutions span fourteen orders of magnitude, and no linear axis can show that.
Where lab results and calculated results part company
These relations describe ideal behaviour: ideal gases, complete reactions, fully dissociated strong acids, no side products. Real yields fall short, real gases deviate near condensation, and real solutions show activity effects at higher concentrations. The calculated figure is the target to compare a measurement against, not a prediction of what the flask will contain.
The formula
pH = −log₁₀[H⁺], and pH + pOH = 14 at 25 °C
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the pH Calculator
- Fill in each field with your own figures — the defaults are only there as an example.
- The result updates as you type, so there is no button to press.
- Check the breakdown under the main result for the supporting numbers.
- Use the copy button to take the result with you, or share the link to reload the same inputs.
pH Calculator — frequently asked questions
Is this ph calculator free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
How accurate is the result?
The maths is exact for the formula shown on the page. Accuracy in the real world depends on your inputs and on assumptions the formula cannot see, so treat the output as a well-grounded estimate rather than a quote.
Can I use it on my phone?
Yes. The page is responsive, weighs a few kilobytes and works offline once loaded, so it behaves the same on a phone as on a desktop.
What people search for
This page answers each of these searches. They are the exact phrases visitors use to find the ph calculator.
- h+ calculator from ph
About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed September 14, 2026 · Calculation runs client-side · No data collected · Report an error