pH measures the concentration of hydrogen ions (H⁺) in solution on a logarithmic scale. Each pH unit represents a 10-fold change in acidity—pH 4 is 10 times more acidic than pH 5, and 100 times more acidic than pH 6. This scale was invented because hydrogen ion concentrations span an enormous range (from 10⁰ to 10⁻¹⁴ M) that would be impractical to work with directly.
The calculator uses the fundamental relationships: pH = -log₁₀[H⁺], pOH = -log₁₀[OH⁻], and pH + pOH = 14 (at 25°C). The water dissociation constant Kw = [H⁺][OH⁻] = 10⁻¹⁴ ensures these values are mathematically linked. Input any one parameter and the calculator derives the others through these chemical equalities.
Most biological processes are extremely sensitive to pH. Enzymes, which catalyze life's reactions, often have a specific 'optimum pH' where they function best. Outside this range, they can denature (lose their shape) and stop working. This is why the human body has strict mechanisms (buffers) to keep blood pH between 7.35 and 7.45.
