Measure the hydrogen ion concentration, [H+]
Use the formula pH = -log10[H+]
If given pOH, use pH = 14 – pOH
If given hydroxide ion concentration, [OH-], calculate pOH = -log10[OH-] first
Use a pH meter or pH indicator paper for direct measurement
Determine whether the solution is acidic, neutral, or basic based on the pH value
For strong acids or bases, use complete dissociation to find ion concentration
For weak acids or bases, use equilibrium expressions to find ion concentration
For buffered solutions, use the Henderson-Hasselbalch equation
Verify the temperature if high accuracy is needed