pH Calculator
Calculate pH from hydrogen ion concentration [H⁺], or find [H⁺] and [OH⁻] from a known pH value. Supports acids and bases.
pH
—
pOH —
[H⁺] mol/L —
[OH⁻] mol/L —
Classification —
How to Use This Calculator
- Select whether you are converting from [H⁺] concentration to pH or from pH to concentration.
- Enter the known value.
- Results show pH, pOH, [H⁺], and [OH⁻] with solution classification.
Formula
pH = −log₁₀[H⁺]
[H⁺] = 10^(−pH)
pOH = 14 − pH | [OH⁻] = 10^(−pOH)
Example
Example: [H⁺] = 1×10⁻⁴ mol/L → pH = 4 (acidic) → pOH = 10, [OH⁻] = 10⁻¹⁰ mol/L.
Frequently Asked Questions
- pH = −log₁₀[H⁺], where [H⁺] is the hydrogen ion concentration in mol/L. pH 7 is neutral; below 7 is acidic; above 7 is basic (alkaline).
- Pure water at 25°C has a pH of 7.00 because [H⁺] = [OH⁻] = 1.0 × 10⁻⁷ mol/L.
- pOH = −log₁₀[OH⁻]. For any aqueous solution at 25°C, pH + pOH = 14.
- White vinegar (about 5% acetic acid) has a pH of approximately 2.4–3.0.
- Use pH = −log₁₀([H⁺]). For example, [H⁺] = 0.001 mol/L → pH = −log(0.001) = 3.