pH Calculator (from [H⁺])
pH = -log[H⁺]. Compute pH from hydrogen-ion concentration in mol/L.
Result
pH
7.000
Roughly neutral. pOH = 7.000.
- [H⁺]1.000e-7 mol/L
- pH7.0000
- pOH7.0000
- [OH⁻]1.000e-7 mol/L
- ClassificationRoughly neutral
Step-by-step
- pH = -log₁₀[H⁺] = -log(1.000e-7) = 7.0000.
- pOH = 14 - pH = 7.0000.
- [OH⁻] = 10⁻ᵖᴼᴴ = 1.000e-7 mol/L.
How to use this calculator
- Enter [H⁺] in mol/L (often a small number like 1e-7).
- Read pH and the calculated pOH and [OH⁻].
About this calculator
pH is a logarithmic measure of hydrogen-ion concentration: pH = −log[H⁺]. Pure water at 25°C has [H⁺] = 10⁻⁷ mol/L → pH = 7 (neutral). Acidic: pH < 7. Basic: pH > 7. The relationship pH + pOH = 14 holds at 25°C in water.
Frequently asked
Water self-ionizes slightly: H₂O ⇌ H⁺ + OH⁻. At 25°C, [H⁺] = 10⁻⁷ M, so pH = 7. Higher temperature shifts pH of pure water down (still neutral, but lower number).
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