pH and pOH Calculator

About this calculator

pH and pOH measure how acidic or basic a solution is using negative log-base-10 scales: pH = −log₁₀[H⁺] and pOH = −log₁₀[OH⁻]. At 25°C, the two always sum to 14, because water's ion product constant Kw = [H⁺][OH⁻] = 1×10⁻¹⁴ links them — so knowing one instantly gives the other.

Chemistry students use this relationship constantly when titrating acids and bases in lab, biologists monitor pH because human blood must stay within a narrow 7.35–7.45 range for enzymes to function, and environmental scientists and agronomists test soil and water pH because it governs nutrient availability and aquatic-life tolerance. Enter the hydrogen-ion concentration to get both values at once.