pH Scale
The conventional scale, usually running from 0 to 14, on which the acidity or alkalinity of aqueous solutions is expressed.
Formula / equation
0 (acidic) – 7 (neutral) – 14 (alkaline)
Unit
Dimensionless
In depth
The familiar range simply reflects the practical limits of ordinary aqueous solutions; concentrated strong acids can give negative pH values and concentrated alkalis can exceed 14. The scale is measured with a glass electrode calibrated against standard buffers.
Examples in the real world
Universal indicator shading from red at pH 1 through green at 7 to violet at 14.