Four calculators, one panel.
Pick a mode below — mix and match units freely, everything recalculates live as you type, and every result explains itself.
Molar concentration, in moles per litre or a smaller unit.
Most everyday solutions fall between 0 and 14.
Most everyday solutions fall between 0 and 14.
Two inputs to an answer.
No manual required — but here's the entire flow in four moves.
Pick a mode
pH & pOH for a known ion concentration. Conc. from pH or Conc. from pOH for the two reverse cases. Dilution for working out C1V1 = C2V2 on its own.
Enter what you know
Type a number and pick its unit from the dropdown next to it — M, mM or µM for concentration, L, mL or µL for volume. The example chips fill everything in with one tap.
Read the results
The main answer sits up top in large type. Related values — pOH, the other ion, or the acidic/basic call — sit below, and the exact formula with your numbers substituted sits at the bottom.
Trust the checks
Impossible inputs — a negative concentration, or a volume you're trying to divide by zero — get flagged with a plain-English reason instead of a wrong or broken answer. Copy any result set with one click.
Two equations behind every mode.
The pH scale and the dilution equation are the two ideas doing all the work above.
pH from concentration
[H⁺] in moles per litre. Since pH + pOH = 14 at 25°C, either scale gets you the other and both ion concentrations.
Concentration from pH
Reversing the log gives back the hydrogen ion concentration; [OH⁻] follows from Kw = [H⁺][OH⁻] = 1.0×10⁻¹⁴.
Dilution equation
The moles of solute don't change on dilution — only the volume does. Solve for whichever of the four values you're missing.
Questions people actually ask.
The short answers — with the long ones one tap away.
What is the formula for pH?+
pH is pH = -log10[H+], where [H+] is the hydrogen ion concentration in moles per litre. A solution with [H+] = 1×10⁻³ M has pH = -log10(0.001) = 3.
How do I calculate pH from concentration?+
Enter the hydrogen or hydroxide ion concentration in the pH & pOH tab, in M, mM, µM or nM. The calculator applies pH = -log10[H+] and returns pH, pOH, [H+] and [OH-] together, plus an acidic/neutral/basic read.
How do I find concentration from pH?+
Rearrange the formula: [H+] = 10^-pH. Enter the known pH in the Conc. from pH tab and the calculator returns [H+], [OH-] and pOH.
How do I find concentration from pOH?+
Rearrange the formula: [OH-] = 10^-pOH. Enter the known pOH in the Conc. from pOH tab and the calculator returns [OH-], [H+] and pH.
What is the relationship between pH and pOH?+
At 25°C, pH + pOH = 14, because the ion product of water Kw = [H+][OH-] = 1.0×10⁻¹⁴. Knowing either pH or pOH is enough to find the other and both ion concentrations.
How does the dilution calculator work?+
It uses C1V1 = C2V2, where C1 and V1 describe the stock solution and C2 and V2 describe it after dilution. Pick which value you need in the Dilution tab, enter the other three, and it solves the rest.
Is this tool free, and where does my data go?+
It's completely free and runs entirely in your browser — nothing you type is uploaded, logged, or sent to any server. No account, no sign-up, no limits.