pH Calculator
Calculate pH from hydrogen ion concentration, or work backward from pH to concentration — the core equation of acid-base chemistry.
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How it works
pH = −log₁₀[H⁺]; [H⁺] = 10⁻ᵖᴴFrequently Asked Questions
How do I calculate pH from concentration?
Take the negative base-10 logarithm of the hydrogen ion concentration in mol/L: a concentration of 1×10⁻⁴ M gives pH = 4. Each whole pH unit represents a tenfold change in acidity.
What pH range is acidic, neutral, and basic?
Below 7 is acidic, exactly 7 is neutral (pure water at 25°C), above 7 is basic (alkaline). Battery acid is around pH 0–1; household bleach is around pH 12–13.
Why is pH logarithmic?
Hydrogen ion concentrations span an enormous range (from 1 to 10⁻¹⁴ mol/L), so a log scale compresses that range into manageable numbers — a pH 3 solution has 10× more H⁺ than pH 4, and 100× more than pH 5.