Nernst Equation Calculator

Frequently Asked Questions

• What is the Nernst equation?+
  It is E = E° − (RT/nF) ln Q, which gives the potential of an electrochemical cell away from standard conditions. E° is the standard potential, R the gas constant, T the absolute temperature, n the electrons transferred, F the Faraday constant, and Q the reaction quotient.
• What is n?+
  n is the number of moles of electrons transferred in the balanced cell or half-reaction. For the Daniell cell (Zn + Cu²⁺ → Zn²⁺ + Cu) two electrons move, so n = 2. It must always be entered because it scales the RT/nF term.
• What is the reaction quotient Q?+
  Q is the ratio of product to reactant activities (often approximated by concentrations or partial pressures) at the moment you are interested in. It has the same form as the equilibrium constant K but uses current, not equilibrium, values. Q must be positive because the equation takes its logarithm.
• Do I have to enter a temperature?+
  No. If you leave temperature blank the calculator uses 298.15 K (25 °C), the standard reference. Enter a value in K or °C only if your problem is at a different temperature, since the RT/nF factor changes with T.
• Where does the 0.0592 version come from?+
  Substituting T = 298 K and converting ln to log₁₀ collapses RT/F × 2.303 into about 0.0592 V, giving E = E° − (0.0592/n) log Q. It is just the Nernst equation at room temperature, and this calculator uses the full form so it is correct at any temperature.
• Can it solve for the reaction quotient?+
  Yes. Enter n, the measured potential E and the standard potential E°, and leave Q blank — the calculator rearranges the equation to Q = exp((E° − E)nF/RT). This is how you can work backwards from a measured voltage.
• What happens at equilibrium?+
  At equilibrium the cell can do no more work, so E = 0 and the reaction quotient Q equals the equilibrium constant K. Setting E = 0 in the Nernst equation is the standard way to link E° to K.
• What units does it use?+
  Potentials E and E° are in volts. n and Q are dimensionless. Temperature is in kelvin (you may type °C and the tool converts). The constants R and F are built in.
• What syllabus is this built against?+
  The Tool Information block lists the exact syllabus — Cambridge A-Level Chemistry 9701 and IB Diploma electrochemistry. It is a study aid for checking your working, not a substitute for your official syllabus or teacher.
• Is the Nernst Equation Calculator free?+
  Completely free, with no account or usage limit. It runs entirely in your browser, collects no data, and works offline once the page has loaded.