pH to hydrogen ion concentration
Enter a pH to see the matching hydrogen ion concentration. Handy for acid and base problems and comparing acidity.
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How to use it
- Enter ph value.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
[H+] = 10^(−pH); pOH = 14 − pH; [OH−] = 10^(−pOH).
Example
Inputs: pH value = 4.5. Result: Hydrogen ion [H+]: 0.0000316228 mol/L; Hydroxide [OH−]: 3.16228e-10 mol/L; pOH: 9.5.
Limits and caveats
- pH + pOH = 14 holds at 25 °C only.
- The result equals activity, which matches concentration only in dilute solutions.
Questions about this tool
What is [H+] at pH 3?
10^-3, which is 0.001 mol/L.
How much does [H+] change when pH drops by 1?
It rises tenfold, because the scale is logarithmic.
Can I enter decimals such as 4.5?
Yes. At pH 4.5 the result is about 3.162 × 10^-5 mol/L.