pH Calculator
pH and pOH from hydrogen ion concentration — or concentration from pH.
pH Calculator
| pH | 7.000 |
| pOH | 7.000 |
| [H⁺] concentration | 0.0000001000 mol/L |
| [H⁺] (scientific notation) | 1.000e-7 mol/L |
| Solution is | Neutral |
Pure water with [H⁺] = 1×10⁻⁷ mol/L has pH 7.00 and pOH 7.00 — neutral.
pH measures acidity on a logarithmic scale: pH = −log₁₀[H⁺], where [H⁺] is the hydrogen ion concentration in mol/L. Each pH unit is a tenfold change in concentration.
Enter a concentration (scientific notation such as 1e-7 is fine) to get pH, pOH and whether the solution is acidic, neutral or alkaline at 25 °C, where pH + pOH = 14. Reverse mode converts a pH value back to [H⁺].
The formula
Worked example
Pure water with [H⁺] = 1×10⁻⁷ mol/L has pH 7.00 and pOH 7.00 — neutral.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
Frequently asked questions
Why is the pH scale logarithmic?
Concentrations span many orders of magnitude (from over 1 mol/L to below 10⁻¹⁴). A log scale compresses that range into the familiar 0–14 window; one pH unit always means a factor of ten.
Can pH be below 0 or above 14?
Yes, for very concentrated strong acids or bases — for example 10 mol/L HCl has pH ≈ −1. The 0–14 range simply covers most dilute aqueous solutions at 25 °C.
Category: Science calculators
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