pH Calculator
Calculate pH from hydrogen ion concentration, or find H+ concentration from pH.
pH Calculator
Calculate pH from hydrogen ion concentration, or find H+ concentration from pH.
Formula
pH = -log10([H+])What is This Tool?
pH is a logarithmic scale from 0 to 14 that measures the acidity or basicity of an aqueous solution. A pH of 7 is neutral (pure water), values below 7 are acidic, and values above 7 are basic (alkaline). Each whole number change represents a tenfold change in hydrogen ion concentration.
Formula
pH = -log10([H+])
pOH = 14 - pH
[H+] = 10^(-pH)
[OH-] = 10^(-pOH)Worked Examples
1. Finding pH of HCl solution
Given: [H+] = 0.001 M
pH = -log10(0.001)
pH = -log10(10^-3)
pH = 3.0
Result: pH = 3.0 (acidic)
2. Finding [H+] from pH
Given: pH = 5.5
[H+] = 10^(-5.5)
[H+] = 3.162 x 10^-6 M
Result: [H+] = 3.162 x 10^-6 M
3. Household ammonia
Given: pH = 11.5
pOH = 14 - 11.5 = 2.5
[OH-] = 10^(-2.5) = 0.00316 M
[H+] = 10^(-11.5) = 3.16 x 10^-12 M
Result: Strongly basic
Frequently Asked Questions