Electrolysis Calculator — Faraday's Laws
Calculate the mass of a substance deposited or dissolved at an electrode during electrolysis. Enter current, time, molar mass and ionic charge to apply Faraday's first and second laws with optional current efficiency.
A
s
g/mol
%
Mass of substance deposited or dissolved at the electrode
- 1
Charge passed Q = I × t
2 A × 3,600 s = 7,200 - 2
Moles deposited: Q_eff ÷ (n × F)
7,200 ÷ (2 × 96 485) = 0.037311 - 3
Mass deposited: moles × M
0.037311 mol × 63.55 g/mol = 2.3711
How does this calculator work?
By Faraday's laws, deposited mass m = (M × I × t) / (n × F), where M is molar mass, I is current, t is time in seconds, n is ionic charge and F = 96 485 C/mol. Copper (M=63.55, n=2) at 2 A for 1 hour at 100% efficiency: m ≈ 2.37 g.
Formula
How this is calculated
Faraday's first law states that the mass deposited at an electrode is directly proportional to the total electric charge passed through the electrolyte. The charge Q in coulombs equals current I (amperes) multiplied by time t (seconds): Q = I × t. Faraday's second law then connects charge to amount of substance: the moles deposited = Q ÷ (n × F), where n is the valence number (the ionic charge — the number of electrons exchanged per ion) and F = 96 485 C/mol is the Faraday constant (the charge carried by one mole of electrons). Multiplying the moles by the substance's molar mass M gives the deposited mass m in grams.
The valence number n is determined by the half-reaction. For copper plating from CuSO₄ solution (Cu²⁺ + 2e⁻ → Cu), n = 2. For silver from AgNO₃ (Ag⁺ + e⁻ → Ag), n = 1. For aluminium from Al³⁺, n = 3. A higher n means more charge is needed to deposit the same number of moles, since each ion requires more electrons.
In practice, side reactions — mainly water electrolysis producing H₂ or O₂ — consume some of the current without contributing to the desired deposition. Entering a current efficiency below 100% (typically 85–99% for industrial copper or nickel plating) scales the effective charge accordingly. Leave efficiency at 100% for the ideal Faraday calculation.
Frequently asked questions
The Faraday constant (F = 96 485 C/mol) is the electric charge carried by one mole of electrons — the product of the elementary charge (1.602 × 10⁻¹⁹ C) and Avogadro's number (6.022 × 10²³ /mol). It is the fundamental bridge between electrical charge measured in coulombs and chemical amounts measured in moles.
The valence number n is the number of electrons transferred per ion in the electrode half-reaction. Write the balanced half-reaction and count the electrons on the left-hand side: Cu²⁺ + 2e⁻ → Cu gives n = 2; Ag⁺ + e⁻ → Ag gives n = 1; Fe³⁺ + 3e⁻ → Fe gives n = 3.
Side reactions — most commonly hydrogen evolution (2H⁺ + 2e⁻ → H₂) at the cathode or oxygen evolution at the anode — consume electrons without contributing to the target deposit. Ohmic heating, poor ion transport and electrode surface effects also reduce yield. Enter your process current efficiency to get a more realistic estimate.
TG we-Calculate Editorial Team. (2026). Electrolysis Calculator — Faraday's Laws [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/electrolysis-calculator
TG we-Calculate Editorial Team. "Electrolysis Calculator — Faraday's Laws." TG we-Calculate. 2026. https://we-calculate.com/calculator/electrolysis-calculator.
TG we-Calculate Editorial Team, "Electrolysis Calculator — Faraday's Laws," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/electrolysis-calculator
@misc{wecalculate_electrolysis_calculator, title = {Electrolysis Calculator — Faraday's Laws}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/electrolysis-calculator}}, year = {2026}, note = {TG we-Calculate} }
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