pH Calculator
Inputs
Enter a pH value or ion concentration to calculate acidity/basicity.
What is pH?
pH is a measure of how acidic or basic a solution is. The term stands for "potential of hydrogen" and represents the negative logarithm of the hydrogen ion concentration: pH = -log₁₀[H⁺].
The pH scale ranges from 0 to 14. A pH of 7 is neutral (pure water). Values below 7 are acidic; values above 7 are basic (alkaline).
Key Formulas
pH = -log₁₀[H⁺]pOH = -log₁₀[OH⁻]pH + pOH = 14 (at 25°C)[H⁺] × [OH⁻] = 10⁻¹⁴ (Kw at 25°C)pH Scale Examples
| Solution | pH | Nature |
|---|---|---|
| Battery Acid | ~0 | Acidic |
| Lemon Juice | ~2 | Acidic |
| Coffee | ~5 | Acidic |
| Pure Water | 7 | Neutral |
| Blood | ~7.4 | Basic |
| Baking Soda | ~9 | Basic |
| Bleach | ~13 | Basic |
Frequently Asked Questions
Can pH be negative or above 14?
Yes, for very strong acids (e.g., concentrated HCl) pH can be negative. For very strong bases, pH can exceed 14.
Why is pH important in biology?
Enzymes and biological processes are highly pH-sensitive. Human blood must maintain a pH near 7.4 for survival.