Chemistry

pH & pOH Calculator

Calculate pH and pOH from hydronium ion concentration at 25 °C.

Explore foundational chemistry calculators

Move between molarity, dilution, amount of substance, gases, acid-base calculations, solution composition and reaction yield.

Share this calculator
WhatsApp

pH & pOH Calculator is an educational chemistry tool for applying standard introductory quantitative relationships.

How it works

Enter the required values in the units shown. The calculator validates the numerical domain and applies pH = −log₁₀[H₃O⁺]; pOH = 14 − pH at 25 °C.

The formula

pH = −log₁₀[H₃O⁺]; pOH = 14 − pH at 25 °C

Variables: [H₃O⁺] = Hydronium concentration (mol/L).

Worked example

Example: [H₃O⁺] = 1×10⁻³ mol/L → pH = 3 and pOH = 11 at 25 °C.

Frequently asked questions

What is this chemistry calculator useful for?

It is designed for studying introductory chemistry, checking exercises and understanding the relationship between the entered quantities.

Do the units matter?

Yes. Use the units displayed beside each field. A formula is only dimensionally meaningful when compatible units are used.

Last content reviewSeptember 25, 2026
Editorial reviewHe-Sab Editorial Review

Sources and references

These sources are used to verify terminology, formulas, and information related to this calculator.