pH Calculator

Determine the acidity or alkalinity of a solution

Use decimal (0.001) or scientific notation (1e-3)

OR

pH Value:

pOH Value:

Solution Type:

H+ Concentration: mol/L

OH- Concentration: mol/L

Understanding the pH Scale and Calculations

The pH calculator is an essential tool for chemists, students, and pool owners alike. It measures the "Potential of Hydrogen," which represents the concentration of hydrogen ions in a water-based solution. The scale typically ranges from 0 to 14, providing a logarithmic measurement of how acidic or basic (alkaline) a substance is.

The Mathematical Formulas Behind pH

The relationship between pH and hydrogen ion concentration is defined by the following logarithmic equations:

• pH Formula: pH = -log₁₀[H⁺]
• pOH Formula: pOH = -log₁₀[OH^–]
• The Relationship: pH + pOH = 14 (at standard room temperature, 25°C)

Because the scale is logarithmic, each whole pH value below 7 is ten times more acidic than the next higher value. For example, a solution with a pH of 4 is ten times more acidic than a solution with a pH of 5 and one hundred times more acidic than a pH of 6.

Interpreting Your Results

Once you enter the concentration in moles per liter (M), the calculator classifies the solution based on the result:

• Acidic (pH 0 to 6.9): Solutions with a high concentration of hydrogen ions. Common examples include lemon juice, battery acid, and coffee.
• Neutral (pH 7.0): Pure water is the standard for neutrality, where the concentration of H⁺ and OH^– ions are perfectly balanced.
• Basic/Alkaline (pH 7.1 to 14): Solutions with a lower concentration of hydrogen ions (and higher hydroxyl ions). Examples include bleach, soapy water, and ammonia.

Calculation Examples

Example 1: Acidic Solution
If you have a solution with a hydrogen ion concentration [H⁺] of 0.01 mol/L:
pH = -log(0.01) = 2.0. This is a strongly acidic solution.

Example 2: Basic Solution
If the concentration of [OH^–] is 1.0 x 10^-3 mol/L:
pOH = -log(10^-3) = 3.0.
pH = 14 – 3.0 = 11.0. This is a basic (alkaline) solution.

Why Use a pH Calculator?

Accurate pH calculation is critical in various fields. In agriculture, soil pH determines nutrient availability for plants. In medicine, blood pH must be strictly maintained around 7.4 for human survival. In industrial settings, pH control prevents pipe corrosion and ensures the efficacy of chemical reactions. Using this digital tool eliminates manual logarithmic errors and provides instant conversion between [H⁺], [OH^–], pH, and pOH.