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pH to Hydrogen Concentration Calculator

Hydrogen Ion Concentration: [H+] = 10^(-pH) mol/L

Example: A pH of 7 (neutral pure water) corresponds to [H+] = 1.0 × 10^-7 mol/L.

pH Input

Concentration

Hydrogen Ion [H+] 1.0e-7 mol/L
Hydroxide Ion [OH-] 1.0e-7 mol/L

Understanding the pH Scale

pH stands for "potential of hydrogen" and is a logarithmic measure of hydrogen ion [H+] concentration in a solution. The scale runs from 0 to 14, where each unit represents a 10-fold change in [H+].

pH 0: [H+] = 1.0 mol/L (strong acid, battery acid)
pH 7: [H+] = 10⁻⁷ mol/L (neutral, pure water)
pH 14: [H+] = 10⁻¹⁴ mol/L (strong base, lye)
Log scale: pH 3 is 10× more acidic than pH 4

pH in Everyday Applications

Water treatment: Municipal water targets pH 6.5-8.5 for safety and pipe protection. Swimming pools: Ideal pH is 7.2-7.8 to minimize chlorine odor and eye irritation. Agriculture: Soil pH 6.0-7.0 optimizes nutrient availability for most crops.

Food & Beverage: Stomach acid (pH 1-3) aids digestion. Coffee is pH 4.8-5.2. Baking soda solutions (pH 8-9) neutralize acid spills. Medicine: Blood pH is tightly regulated at 7.35-7.45 — deviations below 6.8 or above 7.8 are life-threatening.

Frequently Asked Questions — pH Conversion

How do you convert pH to hydrogen ion concentration?
Use the formula [H+] = 10^(-pH) mol/L. Example: pH 3 → [H+] = 10^(-3) = 0.001 mol/L = 1.0 × 10⁻³ mol/L. This is the inverse of pH = −log₁₀[H+].
What is the pH of pure water?
Pure water at 25°C has a pH of exactly 7.0 (neutral), corresponding to [H+] = 1.0 × 10⁻⁷ mol/L. At higher temperatures, water autoionizes more, so pH decreases slightly — but remains neutral because [H+] still equals [OH−].
What does a pH value tell you?
pH indicates how acidic or basic a solution is on a logarithmic scale from 0 to 14. Each pH unit represents a 10× change in hydrogen ion concentration. pH < 7 is acidic, pH = 7 is neutral, pH > 7 is basic (alkaline).
What is the relationship between pH and pOH?
pH + pOH = 14 at 25°C. pOH = −log₁₀[OH⁻]. For neutral water: pH = 7, pOH = 7. For acidic solution: pH < 7, pOH > 7. For basic solution: pH > 7, pOH < 7.
How accurate are pH meters?
Laboratory pH meters achieve ±0.01 pH accuracy with proper calibration. Handheld units are typically ±0.05 to ±0.1 pH. Calibration with buffer solutions (pH 4.0, 7.0, 10.0) is essential. Temperature compensation improves accuracy — the Nernst equation shows pH response changes with temperature.

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