Nernst Equation Calculator

Calculate electrochemical cell potential under non-standard conditions using standard cell potential, temperature, electrons transferred, and reaction quotient.

Instant Potential Any Temperature Electrochemistry

Calculate Cell Potential

Enter the values below to apply the Nernst equation.

Nernst Equation: E = E° − (RT / nF) ln(Q). Temperature must be expressed in Kelvin and the reaction quotient Q must be greater than zero.

Standard Cell Potential (E°)

Standard potential of the electrochemical cell.

Temperature (T)

Temperature is automatically converted to Kelvin.

Electrons Transferred (n) Enter the number of electrons transferred in the balanced redox reaction.

Reaction Quotient (Q) Q is dimensionless and must be greater than zero.

General Nernst Equation
E = E° − (RT / nF) ln(Q)
R = 8.314462618 J/(mol·K) and F = 96485.33212 C/mol.

Cell Potential (E)

volts (V)

Standard E° -

Temperature -

Electrons (n) -

Reaction Q -

Electrochemistry Guide

What Is the Nernst Equation?

The Nernst equation relates the potential of an electrochemical cell to its standard potential, temperature, number of electrons transferred, and reaction quotient.

It is particularly useful when the electrochemical system is operating under non-standard conditions, where concentrations or activities differ from their standard-state values.

Main Formula

Nernst Equation Formula

The general form of the Nernst equation uses the natural logarithm of the reaction quotient.

E = E° − (RT / nF) ln(Q) E = Cell Potential • E° = Standard Cell Potential • R = Gas Constant • T = Kelvin Temperature
n = Electrons Transferred • F = Faraday Constant • Q = Reaction Quotient

At 25°C

Nernst Equation at 25°C

At approximately 25°C (298.15 K), the Nernst equation can also be written using a base-10 logarithm.

E ≈ E° − (0.05916 / n) log₁₀(Q) This simplified form applies at approximately 298.15 K.

How It Works

How to Use the Nernst Equation Calculator

Enter E° and Temperature

Enter the standard cell potential and the temperature of the electrochemical system.

Enter n and Q

Add the number of electrons transferred and the dimensionless reaction quotient.

Calculate E

Click the calculate button to find the cell potential under the entered conditions.

Formula Variables

Nernst Equation Variables

Symbol	Meaning	Unit / Type
E	Cell potential under current conditions	V
E°	Standard cell potential	V
R	Universal gas constant	8.314462618 J/(mol·K)
T	Absolute temperature	K
n	Number of electrons transferred	Dimensionless
F	Faraday constant	96485.33212 C/mol
Q	Reaction quotient	Dimensionless

Worked Example

Nernst Equation Calculation Example

Suppose an electrochemical cell has a standard potential of 1.10 V, transfers two electrons, operates at 25°C, and has a reaction quotient Q = 0.01.

At 298.15 K, substitute these values into the Nernst equation.

E = 1.10 − [(RT / 2F) ln(0.01)] E ≈ 1.159 V

Understanding Q

How Reaction Quotient Affects Cell Potential

Q < 1

Because ln(Q) is negative when Q is below 1, the Nernst correction can make E greater than E° for the reaction as written.

Q = 1

Since ln(1) = 0, the correction term disappears and the calculated cell potential equals E°.

Q > 1

Since ln(Q) is positive when Q exceeds 1, the correction term lowers E relative to E° for the reaction as written.

Important: The reaction quotient must correspond to the balanced reaction used for the value of n and the standard potential E°.

Applications

Where Is the Nernst Equation Used?

The Nernst equation is widely used in electrochemistry to understand how chemical conditions influence electrode and cell potentials.

Electrochemical Cells

Estimate cell potentials when a system differs from standard-state conditions.

Concentration Effects

Study how changes in chemical activities or effective concentrations influence potential.

Chemistry Education

Check electrochemistry calculations and learn how E, E°, temperature, n, and Q are related.

Frequently Asked Questions

Nernst Equation Calculator FAQs

What is the Nernst equation?

The Nernst equation relates electrochemical cell potential to standard cell potential, temperature, electrons transferred, and the reaction quotient.

What is the general Nernst equation formula?

The general form used by this calculator is E = E° − (RT/nF) ln(Q).

What is the Nernst equation at 25°C?

At 25°C, it can be written approximately as E = E° − (0.05916/n) log10(Q), with potential measured in volts.

What does n mean in the Nernst equation?

The variable n represents the number of electrons transferred in the balanced electrochemical reaction.

What is Q in the Nernst equation?

Q is the dimensionless reaction quotient constructed for the balanced reaction. It represents the system's current chemical state relative to equilibrium.

Can Q be zero?

No. The logarithm of zero is undefined, so the numerical Nernst equation requires Q to be greater than zero.

Why does the calculator convert temperature to Kelvin?

The thermodynamic form of the Nernst equation uses absolute temperature, so temperature must be expressed in Kelvin.

What happens when Q equals 1?

When Q = 1, ln(Q) equals zero. Therefore the correction term is zero and E equals E°.

Can the calculated cell potential be negative?

Yes. Depending on the reaction direction and conditions, the calculated potential for the reaction as written can be positive, zero, or negative.