The standard reduction potentials listed in any reference table are only valid at standard-state conditions of 25 C and 1 M. To calculate the cell potential at non-standard-state conditions, one uses the Nernst equation,
E = E (degree) - ((2.303RT)(nF))log Q
where E is the potential in volts, E (degree) is the standard potential in volts, R = 8.314 J/(K mol) is the gas constant, T is the temperature in kelvins, n is the number of moles of electrons transferred, F= 96,500 C/(mol e-) is the Faraday constant, and Q is the reaction quotient.