pH Calculator
Find the pH of a solution from its hydrogen ion concentration — plus pOH, hydroxide concentration, and acid/base classification.
pH
4
Breakdown
- Classification
- Acidic
- pOH
- 10
- OH⁻ concentration (mol/L)
- 0
Last updated:
FAQ
What is the pH formula?
pH = −log₁₀[H⁺], where [H⁺] is the molar hydrogen ion concentration. For example, pure water at 25 °C has [H⁺] = 1×10⁻⁷ mol/L, giving pH 7.
How are pH and pOH related?
At 25 °C, pH + pOH = 14. Once you know one, subtract from 14 to get the other. The hydroxide concentration follows from pOH the same way: [OH⁻] = 10^(−pOH).
Why does the scale stop at 0–14?
It does not, strictly speaking — very concentrated acids can be negative and strong bases above 14. But for dilute aqueous solutions, water's autoionization keeps most everyday values inside the 0–14 window.
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