pH Calculator
Enter the H⁺ concentration as a power of 10 to calculate pH, pOH, and [OH⁻]. Or enter pH directly to find the concentrations.
How to use this ph calculator
- Express your H⁺ concentration as coef × 10⁻ˣ mol/L.
- Enter x in the exponent field and coef in the coefficient field.
- For pure water (10⁻⁷ mol/L): exp=7, coef=1 → pH 7.
- For HCl 0.01 M (10⁻² mol/L): exp=2, coef=1 → pH 2.
Formula
pH = −log₁₀[H⁺]. pOH = 14 − pH (at 25°C). [OH⁻] = 10^(−pOH). pH + pOH = 14.
About the pH Calculator
The pH scale is one of chemistry's most useful concepts — it quantifies something as abstract as 'how acidic is this?' into a simple number. Lemon juice sits at pH 2.0 (~10,000× more acidic than coffee at pH 5.0).
Each pH unit represents a 10-fold change. Going from pH 7 to pH 4 (stomach acid) means 1,000× more H⁺ ions. This is why even tiny pH shifts in blood (normal: 7.35–7.45) are life-threatening.
Frequently asked questions
+What does pH stand for?
pH stands for 'potential of hydrogen' — a logarithmic scale measuring H⁺ concentration. Scale runs 0–14, with 7 neutral, <7 acidic, >7 basic.
+Why is pH logarithmic?
H⁺ concentrations span 14 orders of magnitude. The log scale compresses this into 0–14, where each unit is a 10-fold change in acidity.
+What is pH 7?
Pure water at 25°C: [H⁺] = [OH⁻] = 10⁻⁷ mol/L. Human blood is pH 7.35–7.45 (slightly basic).