Formula
This calculator uses the standard ph calculator formula:
pH Formula
pH = −log₁₀[H⁺]
Frequently Asked Questions
What is pH?
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pH measures the acidity or alkalinity of a solution on a scale of 0–14. pH = −log₁₀[H⁺]. pH < 7 is acidic, pH = 7 is neutral, and pH > 7 is basic.
What is the pH of pure water?
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Pure water at 25°C has a pH of exactly 7.0, because [H⁺] = [OH⁻] = 1×10⁻⁷ mol/L.
How do you calculate pH from hydrogen ion concentration?
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pH = −log₁₀[H⁺]. For example, if [H⁺] = 0.001 mol/L, pH = −log₁₀(0.001) = −(−3) = 3.
What is pOH?
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pOH = −log₁₀[OH⁻]. At 25°C, pH + pOH = 14. So if pH = 3, pOH = 11.
What common substances have low pH?
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Lemon juice ≈ pH 2, stomach acid ≈ pH 1.5–3.5, vinegar ≈ pH 2.5–3. These are strongly acidic.
What is a buffer solution?
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A buffer solution resists changes in pH when small amounts of acid or base are added. Buffers are typically mixtures of a weak acid and its conjugate base.