pH Calculator
Calculate pH from hydrogen ion concentration or convert between pH, pOH, [H+], and [OH-] values.
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Frequently Asked Questions
Why does pH + pOH equal 14?
At 25 degrees C, the ion product of water Kw = [H+][OH-] = 10^-14. Taking -log of both sides gives pH + pOH = 14.
Can pH be negative or above 14?
Yes. Concentrated strong acids can have pH below 0, and concentrated strong bases can exceed 14. The 0-14 range applies to dilute aqueous solutions.