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Nernst Reduction Potential from Activities

Calculate a half-cell reduction potential from activity ratio, temperature and electron count.

Calculator inputs

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Enter the known values in the units shown. Results update as you type.
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With equal reduced and oxidized activities, the logarithmic term is zero. For E₀ = 0.5 V, the reduction potential is also 0.5 V.

E = E₀ − RT/(zF) ln(a_reduced/a_oxidized); R = 8.3144598 J/(mol·K), F = 96485.3399 C/mol.

Enter these known values and leave the other values blank.

Enter dimensionless activities under a common standard state, not uncorrected concentrations unless the ideal-activity approximation is appropriate.
The simple reaction quotient is reduced-form activity divided by oxidized-form activity. More complicated stoichiometry must already be represented in those inputs.
Temperature is absolute internally, electrons transferred must be a positive whole number, and both activities must be positive.
R and F are the captured historical rounded constants stated in the formula. This tool does not claim current CODATA precision or uncertainty propagation.
E₀ must refer to the same reaction, temperature convention and reference electrode as the desired potential.

The logarithm is zero, so E equals E₀.

Only when an ideal-solution approximation is suitable and concentrations are converted to dimensionless standard-state ratios.

Declare the physical or stated approximation domain; captured arithmetic is unchanged.