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pH calculator

Calculate −log₁₀ of hydrogen-ion concentration as an ideal dilute-solution pH estimate.

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Calculate −log₁₀ of hydrogen-ion concentration as an ideal dilute-solution pH estimate.

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Precision and calculation record
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    Formula and assumptions
    Thermodynamic pH uses activity, not concentration. This ideal concentration calculation cannot replace a measurement or account for ionic strength, temperature or buffers. Negative pH is mathematically possible; values are not forced into 0–14.
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    Using pH calculator
    Calculate −log₁₀ of hydrogen-ion concentration as an ideal dilute-solution pH estimate.
    Thermodynamic pH uses activity, not concentration. This ideal concentration calculation cannot replace a measurement or account for ionic strength, temperature or buffers. Negative pH is mathematically possible; values are not forced into 0–14.
    Next: Molarity calculator
    A worked example
    Example inputs: hydrogen-ion concentration (mol/l) = 0.001. pH (ideal concentration model) = 3.
    Before you use the result
    Thermodynamic pH uses activity, not concentration. This ideal concentration calculation cannot replace a measurement or account for ionic strength, temperature or buffers. Negative pH is mathematically possible; values are not forced into 0–14.
    Example results for hydrogen-ion concentration (mol/l)
    These examples use the formula above. They are reference calculations, not recommended settings.
    Hydrogen-ion concentration (mol/L)pH (ideal concentration model)
    0.00053.30102999566
    0.0013
    0.0022.69897000434
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    ToolOctopus. “pH calculator.” Updated 2026-09-26. https://tooloctopus.com/ph-calculator.
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