pH Calculator
Calculate pH from hydrogen ion concentration or vice versa. See pOH, [H⁺], and [OH⁻] values with a reference table of common substances.
pH
7
pOH
7
[H⁺]
1.0000e-7
[OH⁻]
1.0000e-7
pH Scale — Common Substances
| Substance | pH | Type |
|---|---|---|
| Battery acid | 0 | Acidic |
| Lemon juice | 2 | Acidic |
| Vinegar | 2.9 | Acidic |
| Coffee | 5 | Acidic |
| Pure water | 7 | Neutral |
| Baking soda | 8.3 | Basic |
| Bleach | 12.6 | Basic |
| Drain cleaner | 14 | Basic |
💡 How to Calculate pH
What Is pH?
pH is a logarithmic scale used to measure the acidity or basicity (alkalinity) of a solution. The scale runs from 0 (most acidic) to 14 (most basic), with 7 being neutral (pure water). Each unit on the pH scale represents a 10-fold change in hydrogen ion concentration.
This means stomach acid at pH 1 is 1,000,000 times more acidic than pure water at pH 7. Understanding pH is essential in chemistry, biology, environmental science, and many industrial applications.
How to Calculate pH
pH Formulas
[H⁺] = 10^(−pH)
pH + pOH = 14 (at 25°C)
[H⁺] × [OH⁻] = 10⁻¹⁴ (Kw at 25°C)
For example, if [H⁺] = 0.001 M = 10⁻³ M, then pH = −log₁₀(10⁻³) = 3. Conversely, if pH = 5, then [H⁺] = 10⁻⁵ = 0.00001 M.
pH of Common Substances
Battery acid: pH ≈ 0. Stomach acid: pH ≈ 1.5–3.5. Lemon juice: pH ≈ 2. Vinegar: pH ≈ 3. Coffee: pH ≈ 5. Pure water: pH = 7. Baking soda: pH ≈ 9. Bleach: pH ≈ 12.5. Drain cleaner: pH ≈ 14.