pH Converter
Convert between pH, pOH, hydrogen ion (H+) concentration, and hydroxide (OH-) concentration.
Type in any field — the others update instantly.
pH measures acidity or alkalinity on a scale from 0 to 14.
Core formulas:
- pH = -log₁₀[H⁺]
- pOH = -log₁₀[OH⁻]
- pH + pOH = 14 (at 25°C)
- [H⁺] = 10⁻ᵖᴴ mol/L
- [OH⁻] = 10⁻ᵖᴼᴴ mol/L
- [H⁺] × [OH⁻] = 10⁻¹⁴ (water ionization constant at 25°C)
The pH scale:
| pH | Type | Example |
|---|---|---|
| 0 | Strong acid | Battery acid |
| 2 | Acid | Lemon juice |
| 4 | Weak acid | Tomato juice |
| 7 | Neutral | Pure water |
| 10 | Weak base | Baking soda solution |
| 12 | Base | Soapy water |
| 14 | Strong base | Drain cleaner |
Important: Each whole pH unit represents a 10× change in H⁺ concentration. pH 3 is 10 times more acidic than pH 4. pH 3 is 100 times more acidic than pH 5.