The EMF of a galvanic cell can be calculated using the Nernst equation, which relates the cell potential to the concentration of reactants and products. 

The general form of the equation is:

E = E° - (RT/nF) ln Q

were,

• E° is the standard cell potential
• R is the universal gas constant
• T is the temperature in Kelvin
• n is the number of moles of electrons exchanged
• F is Faraday's constant.