Hydrogen Ion Concentration Calculator

Work out hydrogen ion concentration instantly with clear inputs, formula shown and shareable results.

About Hydrogen Ion Concentration Calculator

pH is defined as the negative base-ten logarithm of the hydrogen ion concentration, so inverting it is a matter of raising ten to the negative pH. A pH of 7 gives exactly 1e-7 mol/L, and the hydroxide concentration follows from Kw = [H+][OH-], which at 25 C is 1.0e-14.

Formulas

Hydrogen ion concentration

[H+] = 10^-pH

Hydroxide from Kw

[OH-] = Kw / [H+]

Worked example

With the default values below, Hydrogen Ion Concentration Calculator returns Hydrogen Ion Concentration of 1.0000 × 10⁻⁷. Change any input above and every figure here is recalculated in your browser.

Inputs used

pH of the solutionaccepts -2–18: 7
Ion product of water Kwminimum 0: 0

Results

Hydrogen Ion Concentration: 1.0000 × 10⁻⁷
Hydroxide Ion Concentration: 1.0000 × 10⁻⁷
pOH: 7.000
Character: Neutral

Step by step

1Values used
2Hydrogen ion concentration
3Hydroxide from Kw
4Hydrogen Ion Concentration= 0.0000
5Hydroxide Ion Concentration= 0.0000
6pOH= 7.000
7Character= Neutral

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What is [H+] at pH 7?

Exactly 1x10^-7 mol/L, and [OH-] is the same, which is what makes pH 7 neutral at 25 C.

Why is Kw an input?

Because it is temperature dependent. At 50 C Kw is about 5.5e-14, so neutral pH is nearer 6.6 than 7.