# pH↔Hydrogen Ion Concentration Converter (\[H⁺\] = 10^(−pH)) Convert pH ↔ [H⁺] in mol/L, mmol/L, µmol/L or nmol/L with the full unit table — pH 7.40 ↔ 39.8 nmol/L. > Canonical page: https://elysiatools.com/en/tools/ph-to-hydrogen-ion - **Category:** Math & Numbers - **Keywords:** ph to hydrogen ion, hydrogen ion concentration, ph calculator, h+ concentration, nmol/l, acid base, blood gas, ph conversion, logarithm ph, chemistry converter ## Overview The pH↔Hydrogen Ion Concentration Converter performs bidirectional conversions between pH and hydrogen ion concentration [H⁺] using the formulas [H⁺] = 10^(−pH) and pH = −log₁₀[H⁺]. It supports multiple concentration units including mol/L, mmol/L, µmol/L, and nmol/L with configurable decimal precision. ## Inputs - **Input Quantity** (select): Whether the entered value is a pH or a hydrogen ion concentration. - **pH** (number): The pH value (−3 to 16), or the concentration in the selected unit. - **Hydrogen Ion Concentration** (select): Unit of the entered (or reported) hydrogen ion concentration. - **Decimal Places** (number) ## When to use - When interpreting clinical blood gas results and converting arterial pH to \[H⁺\] in nmol/L. - When preparing laboratory buffer solutions requiring precise molar hydrogen ion calculations. - When solving chemistry coursework problems involving logarithmic acid-base equilibria. ## How it works - Select whether your input quantity is a pH value or a hydrogen ion concentration. - Enter the numerical value and pick the desired concentration unit (mol/L, mmol/L, µmol/L, or nmol/L). - Set the target decimal precision to control the rounding of the calculated result. - The tool evaluates the logarithmic or exponential relation and outputs the corresponding pH or \[H⁺\] value. ## Use cases - Clinical acid-base status monitoring by converting blood gas analyzer readings between pH and nmol/L. - Analytical chemistry calculations for titrations, dissociation constants, and stock acid dilutions. - Environmental water quality testing to assess \[H⁺\] levels from measured field pH data. ## Frequently asked questions ### What formula is used to convert pH to hydrogen ion concentration? The converter calculates hydrogen ion concentration using [H⁺] = 10^(−pH) mol/L, scaled to your chosen unit. ### What formula is used to convert \[H⁺\] back to pH? The tool calculates pH using the negative logarithm formula: pH = −log₁₀[H⁺], where [H⁺] is in mol/L. ### Which concentration units are supported? You can convert between mol/L (M), mmol/L (mM), µmol/L (uM), and nmol/L (nM). ### Why is nmol/L commonly used for physiological pH? Human arterial blood pH (7.35–7.45) yields very small molar concentrations (35–45 nmol/L), making nmol/L convenient for clinical evaluation. ### Can this tool handle negative pH values or strong bases? 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