pH Calculator API

pH and acid–base maths as an API, computed locally and deterministically. The ph endpoint converts freely between the four ways of describing acidity — the pH, the pOH, the hydronium-ion concentration [H+] and the hydroxide concentration [OH−]: give any one and it returns the others using pH = −log₁₀[H+], [OH−] = Kw/[H+] and pH + pOH = pKw, and classifies the solution as acidic, neutral or basic. The strong endpoint gives the pH of a strong acid or strong base from its molarity ([H+] = c for an acid, [OH−] = c for a base), warning when the solution is so dilute that water self-ionisation matters. The buffer endpoint applies the Henderson–Hasselbalch equation, pH = pKa + log₁₀([A−]/[HA]), to a buffer from a pKa and the conjugate-base-to-acid ratio (given directly or as two concentrations), and also handles a base buffer from a pKb. Kw defaults to 1×10⁻¹⁴ (25 °C) and can be overridden for other temperatures. Everything is computed locally and deterministically, so it is instant and private. Ideal for chemistry and biology lab tools, titration and buffer-prep apps, water-treatment and aquarium software, and science education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is pH and acid–base chemistry; for solution dilution and molarity use a dilution API.