pH Scale Explained: Acids, Bases, and Buffers
Published Apr 13, 2026 · 6 min read
The pH scale measures how acidic or basic a solution is, from 0 (strongly acidic) to 14 (strongly basic). Each step is a 10× change in acidity.
The Formula
pH = −log₁₀[H⁺]
Common pH Values
| Substance | pH |
|---|---|
| Battery acid | 0-1 |
| Lemon juice | 2.0 |
| Vinegar | 2.5 |
| Coffee | 5.0 |
| Pure water | 7.0 |
| Blood | 7.35-7.45 |
| Baking soda | 8.3 |
| Bleach | 12.5 |
Buffers
Buffers resist pH changes when small amounts of acid or base are added. Blood is buffered at pH 7.4 by the carbonate buffer system. Even a change to pH 7.0 would be life-threatening.
Try it: Use our pH Calculator to convert between pH, pOH, and [H⁺] concentration.