Calculate ph

Convert between pH, pOH, and hydrogen- or hydroxide-ion concentration at the 25 °C classroom reference.

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ToolpH Calculator
Input
Output
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Preview

How it works

The simplified model uses pH = −log₁₀[H⁺], pOH = −log₁₀[OH⁻], and pH + pOH = 14 at 25 °C. Any one supplied quantity determines the other three.

  • Concentrations are mol/L.
  • Activity coefficients and temperature-dependent equilibria are omitted.

Worked example

A pH 3 solution
Mildly acidic, like black coffee
Input
											3
Output
												P h: 3
P oh: 11
Concentration h: 0.001
Concentration oh: 1e-11

When to use this

Teaching labs estimate acidity, pool checks compare pH and hydroxide, and buffer lessons convert pH to pOH.

Edge cases

  • Concentrated solutions can fall outside the simple 0–14 classroom range.
  • Zero hydrogen concentration has no logarithm.
  • At other temperatures pH + pOH is not exactly 14.

References