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Calculation Machine

pH Calculator

pH, pOH and ion concentrations.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
pH
3.5
pOH
10.5
[H⁺]
3.1623e-4 mol/L
[OH⁻]
3.1623e-11 mol/L
Classification
Acidic

Working

  1. 1pH = −log₁₀(3.162e-4) = 3.5

Quick answer

pH = −log₁₀[H⁺], and pH + pOH = 14 at 25°C.

The formula

pH = −log₁₀[H⁺]

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Value3.5
  • GivenpH

Result

  • pH3.5
  • pOH10.5
  • [H⁺]3.1623e-4 mol/L
  • [OH⁻]3.1623e-11 mol/L
  • ClassificationAcidic

How to use the pH Calculator

  1. 1Enter the value you know.
  2. 2Select which quantity it is.
  3. 3Read pH, pOH and both ion concentrations.

Frequently asked questions

Why is pH 7 neutral?

At 25°C water self-ionises so [H⁺] = [OH⁻] = 10⁻⁷ mol/L. At other temperatures neutral pH shifts slightly.

Can pH be negative?

Yes. Concentrated strong acids above 1 M give negative pH values.

About this calculator