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pH Calculator

Enter any one of pH, pOH, [H⁺] or [OH⁻] and get the other three.

  • Free
  • No sign-up
  • Nothing is sent or stored

Concentrations like 1e-7 are accepted.

Result

pH
3
Acidic
pOH
11
[H⁺]
0.001 mol/L
[OH⁻]
1 × 10^-11 mol/L
How it was calculated
  1. pH = −log₁₀[H⁺]
  2. pH + pOH = 14 (at 25 °C)
Assumes 25 °C, where water's ion product Kw = 1.0 × 10⁻¹⁴.

The calculation happens instantly in your browser. The numbers you enter are not sent to our servers or saved.

How to use the pH Calculator

  1. Choose what you know.
  2. Enter the value (concentrations in mol/L, like 1e-3).
  3. Read all four values and whether it's acidic or basic.

What does this tool do?

pH is the negative base-10 logarithm of the hydrogen ion concentration. Each step on the scale is a tenfold change: pH 3 is ten times more acidic than pH 4.

At 25 °C, pH + pOH = 14. Below 7 is acidic, 7 is neutral and above 7 is basic.

Why use it?

  • All four quantities at once.
  • Acid/base classification.
  • Accepts scientific notation.

The formula

pH = −log₁₀[H⁺]
pOH = −log₁₀[OH⁻]
pH + pOH = 14 (25 °C)

Privacy

The calculation happens instantly in your browser. The numbers you enter are not sent to our servers or saved. There's no account to create and nothing to install.

Last reviewed by the M2Toolkit team.

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