Calculate pH from hydrogen ion concentration or find concentration from pH using mol/L, mmol/L, or µmol/L units with step-by-step results.
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mol/L To pH Formula
The following concentration formula approximates pH for an ideal dilute solution with hydrogen-ion activity coefficient equal to 1. Thermodynamic pH is defined using hydrogen-ion activity.
Variables:
- pH is the measure of acidity or alkalinity
- [H+] is the hydrogen ion concentration in mol/L
To calculate the pH, take the negative logarithm (base 10) of the hydrogen ion concentration.
| pH | [H+] (mol/L) | [H+] (mmol/L) | [H+] (µmol/L) |
|---|---|---|---|
| 0 | 1 | 1000 | 1000000 |
| 1 | 0.1 | 100 | 100000 |
| 2 | 0.01 | 10 | 10000 |
| 2.5 | 0.0031623 | 3.16228 | 3162.28 |
| 3 | 0.001 | 1 | 1000 |
| 3.5 | 0.000316228 | 0.316228 | 316.228 |
| 4 | 0.0001 | 0.1 | 100 |
| 5 | 0.00001 | 0.01 | 10 |
| 6 | 0.000001 | 0.001 | 1 |
| 6.5 | 3.16228e-7 | 0.000316228 | 0.316228 |
| 7 | 1e-7 | 0.0001 | 0.1 |
| 7.4 | 3.98107e-8 | 3.98107e-5 | 0.0398107 |
| 7.5 | 3.16228e-8 | 3.16228e-5 | 0.0316228 |
| 8 | 1e-8 | 0.00001 | 0.01 |
| 9 | 1e-9 | 0.000001 | 0.001 |
| 10 | 1e-10 | 0.0000001 | 0.0001 |
| 11 | 1e-11 | 1e-8 | 0.00001 |
| 12 | 1e-12 | 1e-9 | 0.000001 |
| 13 | 1e-13 | 1e-10 | 0.0000001 |
| 14 | 1e-14 | 1e-11 | 0.00000001 |
| Formula: [H+] (mol/L) = 10^-pH; pH = -log10([H+]). Unit relations: 1 mol/L = 1000 mmol/L = 1,000,000 µmol/L. | |||
What is pH?
pH describes the acidity or basicity of an aqueous solution through hydrogen-ion activity. Near 25°C, pH 7 is approximately neutral, lower values are acidic, and higher values are basic; the neutral value changes with temperature. The logarithmic scale means a unit change represents a tenfold change in hydrogen-ion activity. Concentration gives an approximation when its activity coefficient is 1, and pH is not restricted to 0–14.
How to Calculate pH?
The following steps outline how to calculate the pH from the hydrogen ion concentration.
- First, determine the hydrogen ion concentration in mol/L.
- Next, take the negative logarithm (base 10) of the hydrogen ion concentration.
- The result is the pH value of the solution.
- After inserting the values and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Hydrogen ion concentration (mol/L) = 1.0 x 10-3
pH = -log10(1.0 x 10-3) = 3
