Calculate pH from hydrogen ion concentration, and the pOH and hydroxide concentration.
pH is a logarithmic scale, so a change of one unit is a tenfold change in hydrogen ion concentration. The relationship pH + pOH = 14 holds at 25 °C, where the water ionisation constant is 10⁻¹⁴. Because the scale is logarithmic, pH 4 is a hundred times more acidic than pH 6 — not fifty per cent more.
pH
pH = −log₁₀[H⁺]; pH + pOH = 14 at 25 °C
pH = −log₁₀[H⁺]; pH + pOH = 14 at 25 °C pH is a logarithmic scale, so a change of one unit is a tenfold change in hydrogen ion concentration. The relationship pH + pOH = 14 holds at 25 °C, where the water ionisation constant is 10⁻¹⁴.
Because the scale is logarithmic, pH 4 is a hundred times more acidic than pH 6 — not fifty per cent more.
This calculator takes 1 input: Hydrogen ion concentration. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.