pOH Calculator – Calculate pOH and Convert to pH
Use our pOH calculator to find the pOH of a solution from [OH⁻] concentration, or easily convert between pH and pOH. Essential tool for acid-base chemistry problems and laboratory work.
pOH measures the hydroxide ion concentration of a solution. The pOH scale ranges from 0 to 14, just like pH. Low pOH values indicate high [OH⁻] concentration (basic solutions). High pOH values indicate low [OH⁻] concentration (acidic solutions).
pOH Formulas
Where:
- pOH = Measure of hydroxide ion concentration
- [OH⁻] = Hydroxide ion concentration (mol/L)
- pH = Measure of hydrogen ion concentration
pH and pOH Relationship
The sum of pH and pOH always equals 14 at 25°C. This relationship comes from the ion product of water: Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25°C. Taking the negative logarithm gives pH + pOH = 14.
| Solution Type | pH | pOH | [H⁺] vs [OH⁻] |
|---|---|---|---|
| Acidic | < 7 | > 7 | [H⁺] > [OH⁻] |
| Neutral | 7 | 7 | [H⁺] = [OH⁻] |
| Basic | > 7 | < 7 | [H⁺] < [OH⁻] |
Example Calculation
A solution has [OH⁻] = 1 × 10⁻⁴ mol/L. Calculate pOH: pOH = -log₁₀(1 × 10⁻⁴) = 4. Then find pH: pH = 14 - 4 = 10. The solution is basic with pH 10.
Enter values and calculate to see the graph
| [OH⁻] (mol/L) | pOH | pH | Solution Type |
|---|---|---|---|
| 1.0 × 10⁰ | 0 | 14 | Strongly Basic |
| 1.0 × 10⁻⁴ | 4 | 10 | Basic |
| 1.0 × 10⁻⁷ | 7 | 7 | Neutral |
| 1.0 × 10⁻¹⁰ | 10 | 4 | Acidic |
| 1.0 × 10⁻¹⁴ | 14 | 0 | Strongly Acidic |
- Calculating hydroxide concentration in basic solutions
- Determining solution alkalinity directly
- Buffer solution preparation and analysis
- Water treatment and quality testing
- Industrial process control for alkaline solutions
Choose conversion type
Select from OH to pOH, pOH to OH, pH to pOH, or pOH to pH conversions.
Enter your value
Input hydroxide concentration or pH/pOH value. Use scientific notation for concentrations.
View results and graph
Get instant pOH or pH results with a visual graph showing the relationship.
Four conversion modes
Handle any pOH, pH, or OH concentration conversion in one tool.
Visual relationship graph
See the linear pH + pOH = 14 relationship plotted clearly.
Reference table included
Quick lookup for common OH concentrations and their pOH values.
Scientific notation support
Enter values like 1e-7 directly for hydroxide concentrations.
Solution classification
Automatically identifies acidic, neutral, or basic solutions.
How do you calculate pOH?
pOH = -log10[OH]. For [OH] = 1 × 10^-4 M, pOH = -log10(1 × 10^-4) = 4.
What is the relationship between pH and pOH?
pH + pOH = 14 at 25°C. If pH is 5, then pOH = 14 - 5 = 9.
What does pOH measure?
pOH measures hydroxide ion concentration. Low pOH means high OH (basic). High pOH means low OH (acidic).
How do you convert pOH to OH concentration?
Use [OH] = 10^-pOH. For pOH = 4, [OH] = 10^-4 = 0.0001 mol/L.
What is a neutral pOH value?
Neutral solutions have pOH = 7 at 25°C, same as pH. This means [OH] = [H+] = 10^-7 M.
Try our other chemistry calculators: the pH calculator for hydrogen ion calculations, the pKa pKb calculator for acid-base constants, and the Henderson-Hasselbalch calculator for buffer solutions.
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