Convert between pH and hydrogen ion concentration.
How It Works
How pH Calculator Works
pH is defined as the negative base-10 logarithm of the hydrogen ion concentration — this logarithmic scale is why each single-unit change in pH represents a tenfold change in actual acidity, not just a small linear step.
Worked Example
See It In Action
A hydrogen ion concentration of 10⁻⁷ mol/L — the value for pure water — gives a pH of exactly 7, the neutral point on the scale.
FAQ
Frequently Asked Questions
Why is the pH scale logarithmic?
Hydrogen ion concentrations in real solutions span an enormous range, from very dilute to very concentrated — a logarithmic scale compresses that huge range into a compact, manageable set of numbers, typically 0 to 14 for everyday solutions.
What does a change of 1 pH unit actually mean?
It represents a tenfold change in hydrogen ion concentration — a solution at pH 4 is ten times more acidic than one at pH 5, not just "one unit" more acidic.
