What this calculator does
pH from hydrogen ion concentration works out conversion between [H⁺] and pH, with pOH and [OH⁻] at 25 °C. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulapH = −log₁₀[H⁺]; [H⁺] = 10^−pH; pOH = 14 − pH
The inputs explained
| Field | What to enter |
|---|---|
| Known value | Choose from [H⁺] concentration (mol/L), pH value. |
| Value | A number. Starts at 1e-7. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with value
Every other input is held at the calculator’s starting values while value varies. Select any row to load that scenario into the calculator.