pH calculator
Go from pH to H₃O⁺ concentration (and back), with pOH and whether the solution is acidic or basic.
How it works
pH = −log₁₀[H₃O⁺]. At 25 °C: pH + pOH = 14. pH < 7: acidic; 7: neutral; > 7: basic.
Results are for guidance only and do not replace professional advice.
Worked example
With the default values:
- Value3.5
- I knowThe pH
you get:
- pH3.5
- TypeAcidic · like coffee or tomato
- [H₃O⁺]3.162 × 10^-4 mol/L
- [OH⁻]3.162 × 10^-11 mol/L
Frequently asked questions
How does the “pH calculator” tool work?
pH = −log₁₀[H₃O⁺]. At 25 °C: pH + pOH = 14. pH < 7: acidic; 7: neutral; > 7: basic.
What do I need to enter?
Just fill in: value, i know. The result updates as you type.
Can you give an example?
Value: 3.5; I know: The pH → pH: 3.5; Type: Acidic · like coffee or tomato.
Is this calculator free, and is my data private?
Yes. HOD Calc is completely free with no sign-up. The calculation runs in your browser: nothing you type is sent or stored.