What is the formula used?

The tool uses [H+] = 10^(−pH) to go from pH to concentration, and pH = −log₁₀([H+]) for the reverse direction. These are the standard definitions from the Arrhenius and Brønsted-Lowry acid-base models.

What units is the concentration in?

Concentration is expressed in mol/L (molar, M). A neutral solution at 25 °C has [H+] = 1 × 10⁻⁷ mol/L, which corresponds to pH 7.

What is the valid pH range?

The calculator accepts pH values from −2 to 16. Values outside 0–14 are physically possible in highly concentrated solutions, though rare in everyday contexts.

Why does a small pH change make a big [H+] difference?

pH is a logarithmic scale (base 10). A change of 1 pH unit represents a 10-fold change in [H+] concentration. That is why the jump from pH 3 to pH 2 increases [H+] by an order of magnitude.

Does temperature affect the result?

This calculator assumes 25 °C (298 K), the standard reference temperature. At other temperatures the neutral point (Kw) shifts slightly, but the mathematical relationship pH = −log[H+] still holds.

pH to H+ Concentration Calculator

Enter a pH value to get [H+] concentration, or enter [H+] to get pH — instant bidirectional conversion.

Conversion Mode

pH value

Valid range: −2 to 16

Enter a value and click Calculate to see the result.

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Summary

This calculator performs bidirectional conversion between pH and hydrogen ion concentration [H+]. Enter a pH value and it applies the formula [H+] = 10^(−pH) to compute the molar concentration; enter [H+] and it applies pH = −log₁₀([H+]) to return the pH. All computation is done in your browser — no data is sent to any server.

How it works

Select the direction: "pH → [H+]" or "[H+] → pH".
Type your known value into the input field.
The result appears instantly below, along with scientific notation.
A pH scale indicator shows where the value falls on the acid-base spectrum.
Use "Swap" to flip the mode and continue with the computed result.

Use cases

Convert a measured pH reading to hydrogen ion molarity for a lab report.
Calculate pH from a known [H+] concentration in a titration problem.
Verify textbook acid-base calculation answers in chemistry coursework.
Explore how small pH changes correspond to large [H+] shifts.
Prepare buffer solutions by targeting a specific [H+] molarity.
Cross-check results from a benchtop pH meter against calculated values.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu