pH Calculator

pH compresses a vast range of hydrogen ion concentrations into a manageable logarithmic scale. Each unit step represents a tenfold change in acidity — pH 3 is ten times more acidic than pH 4. Swimming pools, blood, soil, wine, and industrial wastewater all get monitored through pH. The definition ties directly to [H⁺] in aqueous solution at 25°C.

pH definition:

pH = −log₁₀[H⁺]

Where [H⁺] is hydrogen ion concentration in mol/L. Equivalently [H⁺] = 10^−pH. For strong monoprotic acids like HCl, [H⁺] ≈ initial acid molarity at moderate dilution. Strong bases: pOH = −log[OH⁻] and pH = 14 − pOH at 25°C (K_w = 10⁻¹⁴).

Enter [H⁺] or molarity of a strong acid/base to get pH. Weak acids need Ka and equilibrium — this tool targets strong electrolyte shortcuts and direct concentration entry. Neutral water at 25°C has pH 7.0 with [H⁺] = 10⁻⁷ M. Gastric acid ~pH 1.5; household bleach ~pH 12.5.

Worked example: 0.010 M HCl (strong acid). [H⁺] = 0.010 M. pH = −log(0.010) = 2.00. 0.050 M NaOH: [OH⁻] = 0.050, pOH = −log(0.050) = 1.30, pH = 14 − 1.30 = 12.70. Diluting 0.10 M HCl tenfold to 0.010 M raises pH by one unit from 1.0 to 2.0 — logarithmic scaling.

Pair with molarity and dilution for concentration prep, and molar mass when converting acid mass to moles. Environmental and biological systems buffer pH — blood stays near 7.4 via carbonate and protein buffers beyond simple strong-acid math.