pH Calculator
Calculate pH and pOH from hydrogen ion concentration.
Assumptions used in this calculation
- 25°C reference: pOH = 14 - pH assumes the standard 25°C water ion product (Kw = 1.0 × 10⁻¹⁴), which shifts slightly at other temperatures.
About this calculator
Hydrogen ion concentrations in real solutions range from around 1 mol/L in strong acids down to 10⁻¹⁴ mol/L in strong bases, a span far too wide to compare usefully on a linear scale, which is exactly why chemists use the logarithmic pH scale instead, but converting a raw concentration into pH requires a base-10 logarithm, a calculation most people can't do reliably in their head. This calculator takes a hydrogen ion concentration [H⁺] in mol/L and computes pH using pH = -log₁₀[H⁺], along with the corresponding pOH using pOH = 14 - pH at the standard 25°C reference temperature. It's useful for chemistry coursework, checking a solution's acidity or basicity from a measured concentration, or verifying results from a titration or pH meter calibration, without needing a scientific calculator's log function or working through logarithm rules by hand.
Worked example
[H⁺] = 1 × 10⁻⁷ mol/L
Result: pH 7, pOH 7 (neutral)
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