Hydrogen Ion Concentration Calculator

pH is a scale used to measure how acidic or alkaline a solution is, and it's directly tied to the concentration of hydrogen ions (H⁺) in that solution. Enter a pH value (0–14) to get the Hydrogen Ion Concentration [H⁺], or enter a known [H⁺] concentration in mol/L to calculate pH — along with pOH, hydroxide ion [OH⁻] concentration, and solution type (acidic, neutral, or alkaline). You can also enable the temperature option to compute [H⁺] for pure water at a specific temperature using the temperature-dependent Kw value.

Leave blank to calculate pH from [H⁺]

Leave blank to calculate [H⁺] from pH

Calculate based on temperature-dependent Kw value

°C

Temperature for pure water calculation

Results

Hydrogen Ion Concentration [H⁺]

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pH Value

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pOH Value

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Hydroxide Ion [OH⁻]

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Solution Type

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Frequently Asked Questions

What is a hydrogen ion?

A hydrogen ion (H⁺) is also known as a proton. In aqueous solutions, it represents the acidic component and determines the pH of the solution. Higher H⁺ concentrations result in lower pH values (more acidic solutions).

How do I find hydrogen ion concentration from pH?

Use the formula [H⁺] = 10^(-pH). For example, if pH = 3, then [H⁺] = 10^(-3) = 0.001 M or 1.0×10⁻³ M. This inverse relationship means lower pH values correspond to higher H⁺ concentrations.

Should I enter both pH and [H⁺] values?

No, enter only one value and leave the other blank. The calculator will compute the missing value automatically. If you enter both, the calculator will use the pH value and recalculate [H⁺].

What does the temperature option do?

The temperature option calculates the hydrogen ion concentration in pure water at different temperatures using the temperature-dependent water dissociation constant (Kw). At 25°C, pure water has [H⁺] = 1.0×10⁻⁷ M.

How is pOH related to pH?

pOH and pH are related by the equation: pH + pOH = 14 (at 25°C). pOH represents the hydroxide ion concentration: pOH = -log[OH⁻]. This relationship helps determine both acidic and basic properties of solutions.

Do acids have more hydrogen ions?

Yes, acids have higher concentrations of hydrogen ions (H⁺) than pure water. Solutions with [H⁺] > 1.0×10⁻⁷ M (pH < 7) are acidic, while those with [H⁺] < 1.0×10⁻⁷ M (pH > 7) are basic.

When should I use scientific notation?

Scientific notation is recommended for very small or very large concentration values. Hydrogen ion concentrations typically range from 10⁻¹⁴ to 10⁰ M, making scientific notation clearer and more precise than decimal notation.

What is the difference between H⁺ and H₃O⁺?

H⁺ and H₃O⁺ (hydronium ion) are effectively the same in aqueous solutions. H₃O⁺ represents a water molecule (H₂O) combined with a hydrogen ion (H⁺), but both notations refer to the same acidic species in solution.