Chemistry

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Hydrogen Ion Concentration Calculator.

Convert pH to hydrogen- and hydroxide-ion concentrations.

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[H⁺]: 1.00e-7 mol/L

[H⁺]

1.00e-7mol/L
[OH⁻]: 1.00e-7 mol/L

[OH⁻]

1.00e-7mol/L
pOH: 7

pOH

7.0000

Educational arithmetic only. Keep units consistent and use measured or explicitly supplied chemistry inputs; this tool does not infer reaction pathways, property tables, or safety guidance.

Use Cases

Determine acidity or basicity strength

Quickly find the exact hydrogen ion concentration for a given pH to understand the strength of an acid or base solution.

Example: For pH 5, [H+] = 1e-5 mol/L, indicating a slightly acidic solution.

Calculate hydroxide concentration in basic solutions

Use the calculator to find the hydroxide ion concentration when you know the pH, useful for studying bases or buffer solutions.

Example: For pH 9, [OH-] = 1e-5 mol/L.

Frequently Asked Questions

How do I convert pH to hydrogen ion concentration?
Use the formula [H+] = 10^(-pH). Enter the pH value in the calculator, and it will compute the hydrogen ion concentration in mol/L. For example, pH 3 gives [H+] = 0.001 mol/L.
What is the relationship between pH and hydroxide ion concentration?
At 25°C, the ion product of water (Kw) is 1.0 × 10^-14. So [OH-] = Kw / [H+]. The calculator uses this to derive hydroxide concentration from the entered pH.
Can I use this calculator for any pH value?
Yes, you can enter any real pH value. The calculator will compute the corresponding hydrogen and hydroxide ion concentrations. Note that typical pH ranges from 0 to 14, but values outside this range are possible for strong acids or bases.

Tips & Common Mistakes

Tips

  • Enter the pH value as a decimal number; the calculator will handle scientific notation for very small concentrations.
  • Remember that pH is a logarithmic scale: a change of 1 pH unit corresponds to a tenfold change in hydrogen ion concentration.
  • For accurate results, ensure the pH value is measured at the same temperature as the ion product constant (usually 25°C).
  • Use the calculator to check your manual calculations or to quickly convert between pH and concentrations in lab work.

Common Mistakes to Avoid

  • Forgetting that pH is the negative logarithm of hydrogen ion concentration, so a higher pH means lower [H+].
  • Confusing hydrogen ion concentration with hydroxide ion concentration; the calculator provides both, but they are inversely related.
  • Assuming the ion product of water is always 1e-14; it varies with temperature, so the calculator's default is for 25°C.

Last updated: August 13, 2026