What is Faraday's constant?

Faraday's constant (F) is 96,485 coulombs per mole of electrons. It represents the charge carried by one mole of electrons and is the fundamental link between electrical charge and chemical change.

What does ion charge (n) mean?

The ion charge (n) is the number of electrons transferred per ion during the electrode reaction. For Cu²⁺ it is 2, for Ag⁺ it is 1, for Al³⁺ it is 3. Using the wrong n gives the wrong mass.

How is gas volume calculated?

Moles of gas = moles of substance deposited. At STP (0 °C, 1 atm), 1 mol of any ideal gas occupies 22.4 L. At SATP (25 °C, 100 kPa), it occupies 24.8 L. The tool shows both.

What is the difference between Faraday's first and second law?

First law: mass deposited is proportional to charge passed (m ∝ Q). Second law: for the same charge, masses deposited of different substances are proportional to their equivalent weights (M/n). The formula m = QM/(nF) combines both.

Why does efficiency matter?

Real cells have side reactions and resistive losses, so the actual mass deposited is less than the theoretical value. Enter a current efficiency (%) to scale the result to realistic conditions.

Can I calculate time instead of mass?

Yes. Switch to "Find charge / time" mode, enter the target mass, and the tool returns the required charge in coulombs and the time at the entered current.

Faraday's Electrolysis Calculator

Enter current, time, and select an element preset to instantly calculate the mass deposited or volume of gas evolved using Faraday's first and second laws.

Electrolysis Parameters

Element / Gas preset

Molar mass M (g/mol)

Ion charge n (e⁻/ion)

Current I (A)

Time

Current efficiency (%)

Select a preset and enter current + time, then click Calculate.

Common element presets

Species	M (g/mol)	n
Cu²⁺	63.55	2
Ag⁺	107.87	1
Zn²⁺	65.38	2
Fe²⁺	55.85	2
Al³⁺	26.98	3
Ni²⁺	58.69	2
Pb²⁺	207.2	2
Au³⁺	196.97	3
H₂↑	2.016	2
O₂↑	32.00	4
Cl₂↑	70.90	2

Summary

Enter current, time, and select an element preset to instantly calculate the mass deposited or volume of gas evolved using Faraday's first and second laws.

How it works

Select an element or gas preset, or enter molar mass (M) and ion charge (n) manually.
Enter the current (A) and electrolysis time (s, min, or h).
The tool computes total charge Q = I × t in coulombs.
Mass deposited is m = Q × M / (n × F), where F = 96,485 C/mol.
For gas products (H₂, O₂, Cl₂), volume at STP (22.4 L/mol) and SATP (24.8 L/mol) is also shown.
Switch to "Charge mode" to find the charge needed to deposit a target mass.

Use cases

Calculate copper mass deposited during electroplating at a given current and time.
Find charge required to deposit a specific mass of silver.
Determine volume of hydrogen or oxygen released during water electrolysis.
Check chlorine gas production in the chlor-alkali process.
Estimate zinc deposition time for galvanizing at a known current.
Verify electrochemical stoichiometry in lab experiments.
Convert coulombs to grams for any metal ion.

Frequently Asked Questions

Last updated: 2026-09-23 · Reviewed by Nham Vu