Electrolysis Calculator
Estimate deposited or reacted mass from electrical current, time, and electron stoichiometry.
01 Set up your calculation
- Enter the current and total electrolysis time.
- Use the molar mass and electron count from the relevant half-reaction.
- Enter the fraction of charge going to the desired product, expressed as a percentage.
02 The relationship
For the assumptions behind these results, read the explanation below. You can also explore Cell EMF and Molar Mass.
Follow the numbers
For copper deposition with 2 A for 1,800 s, M = 63.546 g/mol, z = 2, and 100% efficiency, Q = 3,600 C and m ≈ 1.18549 g.
03 Charge determines the electron amount
An ampere is a coulomb per second. Multiplying constant current by elapsed seconds gives the transferred charge, and dividing by Faraday’s constant gives moles of electrons. The balanced half-reaction specifies how many electrons are needed per product unit.
For Cu²⁺ + 2e⁻ → Cu, use two electrons and the molar mass of copper. For a molecular product, use the electron count and molar mass for that whole product molecule.
04 Account for the actual current path
The ideal result assumes every relevant electron contributes to the intended product. Current efficiency adjusts for competing electrode reactions or other charge losses. An uncertain efficiency makes the resulting mass an estimate.
If current varies over time, use the time-integrated charge or an appropriate time-average current. This calculation does not determine voltage requirements, electrode area, deposit thickness, gas losses, or process operating conditions.
Questions from the notebook
Can the same equation estimate mass loss?
Yes, with the balanced anodic dissolution half-reaction and its electron count.
Why must electron count be a positive integer?
It represents electrons in the selected balanced half-reaction per product unit.
Does 100% efficiency mean the process uses no wasted energy?
No. Current efficiency concerns the share of charge producing the desired substance, not energy efficiency.
References & reading
- OpenStax, Rice University — Electrolysis ↗
Relates current, time, charge, moles of electrons, and deposited or reacted substance.
- NIST — Guide to SI conversion factors ↗
Supports physical unit conversions. Input values are converted to the formula’s base units before calculation.
Our explanations are written for ChemistryCalc. Read how we build and check our tools. These calculations are educational estimates where the underlying model requires assumptions.