How to Use
- Choose input type
Select whether to enter pH, pOH, [H⁺] concentration, or [OH⁻] concentration.
- Enter value
Input the numeric value for your selected parameter.
- View results
Click Calculate to see pH, pOH, [H⁺], and [OH⁻] values.
What is pH?
pH is the negative base-10 logarithm of the hydrogen ion concentration ([H⁺]) in an aqueous solution, a scale that expresses in a single number how acidic or basic a solution is. The term comes from 'power of Hydrogen' and the value typically falls between 0 and 14.
Because it is a logarithmic scale, a decrease of 1 pH unit means [H⁺] increases exactly tenfold. In other words, a pH 4 solution has 10 times more hydrogen ions than a pH 5 solution and 100 times more than a pH 6 solution.
Where is it used?
- Acid–base titrations and equilibrium analysis in chemistry experiments
- Water quality testing, soil acidity management, pool and aquarium maintenance
- Understanding biological pH homeostasis such as blood and stomach acid
Enter just one of the four values — pH, pOH, [H⁺], or [OH⁻] — and this calculator converts all the rest and even tells you whether the solution is acidic, neutral, or basic.
Formula
The two core formulas are as follows.
pH = -log₁₀[H⁺]pH + pOH = 14 (at 25°C)
Here [H⁺] is the hydrogen ion concentration (mol/L) and [OH⁻] is the hydroxide ion concentration, with [H⁺] = 10^(-pH) used for the reverse calculation.
Example: [H⁺] = 1×10⁻³ mol/L
- pH = -log₁₀(1×10⁻³) = 3
- pOH = 14 - 3 = 11
- [OH⁻] = 10^(-11) = 1×10⁻¹¹ mol/L
Since the pH is below 7, this solution is classified as acidic.