pOH Calculator
Calculate pOH from hydroxide ion concentration, and its related pH via pH+pOH=14.
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Introduction
pOH Calculator — Calculate pOH from hydroxide ion concentration, and its related pH via pH+pOH=14. Enter [OH⁻] (mol/L) to get an instant, accurate result.
Formula
pOH = −log₁₀[OH⁻]. Since pH + pOH = 14 at 25°C (from Kw = 1.0×10⁻¹⁴), pH = 14 − pOH.
Step-by-step
- Enter the [OH⁻] (mol/L).
- Click Calculate to see your result instantly.
Real-world example
Example: With [OH⁻] (mol/L) = 0.0001, the pOH Calculator gives P O H: 4, pH: 10, Oh Concentration: 0.0001.
Frequently Asked Questions
Why does pH + pOH equal 14?
At 25°C the ion-product constant of water, Kw = [H⁺][OH⁻] = 1.0×10⁻¹⁴, and taking −log₁₀ of both sides gives pH + pOH = 14.
Does the pH + pOH = 14 relationship hold at any temperature?
No — Kw itself is temperature-dependent, so the sum of 14 is only accurate at 25°C; it shifts slightly at other temperatures.
What inputs does the pOH Calculator need?
You'll need to provide: [OH⁻] (mol/L). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the pOH Calculator?
The pOH Calculator applies the formula exactly as calculated — pOH = −log₁₀[OH⁻]. Since pH + pOH = 14 at 25°C (from Kw = 1.0×10⁻¹⁴), pH = 14 − pOH. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the pOH Calculator free to use?
Yes, the pOH Calculator is completely free, requires no signup, and runs instantly in your browser.
About the pOH Calculator
The pOH Calculator uses a real, verifiable formula — pOH = −log₁₀[OH⁻]. Since pH + pOH = 14 at 25°C (from Kw = 1.0×10⁻¹⁴), pH = 14 − pOH. — so results are accurate every time, not an approximation.