Nernst Equation Calculator
Nernst equation calculator — enter the number of electrons transferred and any two of cell potential, standard potential and reaction quotient, and solve for the third (with optional temperature). For A-Level and IB electrochemistry. Runs in your browser.
Nernst Equation Calculator
Enter n (electrons transferred) and any two of E, E° and Q — the calculator solves the third. Temperature defaults to 298.15 K (25 °C) if left blank.
- Curriculum
- English (global) — Cambridge International + IB
- Built against
- Cambridge International A-Level Chemistry 9701 + IB Diploma (2023–2025) — Electrochemistry
- Unit system
- SI primary; US/imperial readout below
- First published
- 2 Jun 2026
- Last updated
- 2 Jun 2026
View authoritative scientific sources
- CODATA 2018 — gas constant R, Faraday constant F
- IUPAC — electrochemical conventions
- Atkins, Physical Chemistry — the Nernst equation
- Nernst equation — Encyclopædia Britannica
⚠️ Educational use only — see full disclaimer
EDUCATIONAL USE DISCLAIMER
This calculator is provided for educational and reference purposes only. It is not a substitute for instruction from a qualified teacher, your prescribed textbook, or your school's official curriculum materials.
When preparing for examinations, always cross-check our calculations and notation against your current syllabus and your teacher's guidance. Syllabus conventions and accepted notation vary between curricula and may change between examination years.
If you believe any calculation, notation, or curriculum reference in this tool is inaccurate, please let us know via the feedback button. We review feedback promptly and update tools when verified corrections are needed.
RECATOOLS accepts no liability for academic, examination, professional, or research outcomes arising from use of this tool.
How to Use the Nernst Equation Calculator
Enter the number of electrons
n is the number of moles of electrons transferred in the balanced half- or cell reaction — for example 2 for the Daniell cell. It is always required.
Enter two of E, E° and Q
Give any two of the cell potential E, the standard cell potential E°, and the reaction quotient Q. Leave the one you want to find blank.
Set the temperature (optional)
If you leave temperature blank the calculator uses 298.15 K (25 °C). Enter a value in K or °C for non-standard temperatures.
Read the result
The calculator returns the missing quantity in volts (or as a dimensionless Q). The Tool Information block lists the syllabus this is built against.
The Nernst Equation
Nernst Equation
Example: A Daniell cell has E° = +1.10 V and transfers n = 2 electrons. At 298 K with a reaction quotient Q = 10, find the cell potential.
Using E = E° − (RT/nF) ln Q:
E = 1.10 − (8.314 × 298 / (2 × 96485)) × ln 10 ≈ 1.07 V
The Nernst equation gives the potential of an electrochemical cell when the conditions are not standard: E = E° − (RT/nF) ln Q. Here E is the actual cell (or electrode) potential, E° is the standard potential, R is the gas constant (8.314 J/mol·K), T is the absolute temperature, n is the number of electrons transferred, F is the Faraday constant (96 485 C/mol), and Q is the reaction quotient — the ratio of product to reactant activities at that moment. As a reaction proceeds and Q changes, the cell potential drifts away from E° until, at equilibrium, E reaches zero and the cell is "flat".
This calculator works in both directions: give it the standard potential and the reaction quotient to find the actual potential, or give it the measured potential to back out the quotient. Temperature defaults to 298.15 K (25 °C), the usual reference, but you can enter any value because the RT/nF term is temperature-dependent. The reaction quotient Q must be positive, since the equation takes its natural logarithm. All calculation happens in your browser, so nothing you type is uploaded and the tool works offline once loaded.
The Nernst equation is why a battery's voltage sags as it discharges — the reaction quotient climbs and the potential falls.
10 Facts About the Nernst Equation
The Nernst equation: E = E° − (RT/nF) ln Q.
It gives cell potential at non-standard conditions.
At 298 K it is often written E = E° − (0.0592/n) log Q.
At equilibrium E = 0 and Q = K.
F, the Faraday constant, is 96 485 C/mol.
n is the moles of electrons in the balanced reaction.
Named after Walther Nernst (1889).
It explains why a battery's voltage drops as it discharges.
Q uses concentrations (or pressures) at that instant.
This calculator runs in your browser — your working stays private.
Frequently Asked Questions
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
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