Science & Engineering

pH Calculator

Calculates pH from hydrogen ion concentration using pH = -log10[H+], then reports pOH as 14 minus pH. Enter 0.0001 mol/L to get pH 4 and pOH 10.

What this calculator does

The pH Calculator estimates your result instantly from the values you enter, using standard science & engineering formulas. Calculates pH from hydrogen ion concentration using pH = -log10[H+], then reports pOH as 14 minus pH. Enter 0.0001 mol/L to get pH 4 and pOH 10. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate rather than a certified or official figure.

pH Calculator

Result

—
pH
—
pOH

About pH Calculator

This calculator finds the pH of a solution from its hydrogen ion concentration using pH = −log10[H+], and reports the matching pOH as 14 − pH. Enter the [H+] concentration in mol/L to see both values.

Formula & Mathematical Calculation

pH = f([H⁺] Concentration (mol/L))

Calculated according to standard science formulas implemented in the calculator core.

Calculation Example

For [H+] = 0.0001 mol/L: pH = −log10(0.0001). The pH box shows 4 and the pOH box shows 10, with the note pH = -log[H⁺] = 4 (acidic), pOH = 10.

Key Benefits

  • Computes pH from hydrogen ion concentration with pH = -log10[H+]
  • Automatically reports the corresponding pOH as 14 - pH
  • Labels the solution as acidic, basic or neutral
  • Rounds pH and pOH to three decimal places

How to Use this Calculator

  1. Enter the hydrogen ion concentration
    Type the [H+] concentration in mol/L into the input field, for example 0.0001.
  2. Calculate
    Click Calculate to run the pH formula.
  3. Read pH and pOH
    The result shows pH in one box and pOH in the other, plus an acidic, basic or neutral label.

Assumptions & Limitations

What the calculation assumes

  • Every value you enter is treated as an exact, known amount.
  • Any rate or interval you enter is assumed to hold for the whole period unless the form asks for it separately.
  • Results use standard published formulas and account only for the values entered above.
  • Rounding is applied for display; the underlying calculation uses your full precision.
  • Results are returned in the same units you enter, unless the tool states the output unit.

What it does not cover

  • pH Calculator produces a calculated result for reference and learning, not a certified or official measurement.
  • Real-world outcomes differ when tolerances, rounding rules or local standards apply.
  • Definitions and standards vary by region and change over time; verify the convention that applies to your case.
  • Figures are only as accurate as the inputs you supply — check them before acting on the result.
  • For work where the result carries real consequences, confirm it against an authoritative source.

Frequently Asked Questions

After computing pH = -log10[H+], it sets pOH = 14 - pH, using the standard water ion product at 25 C.

The logarithm of zero or a negative number is undefined, so the tool shows an error asking for a concentration greater than 0.

Yes, values like 1e-4 are accepted and treated the same as 0.0001.

It labels the result neutral only when pH equals exactly 7; below 7 is acidic and above 7 is basic.

Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.