Electrolysis uses electrical current to force a chemical reaction that would not happen on its own — most commonly to deposit a metal from solution (electroplating) or to decompose a compound into its elements. This calculator applies Faraday's laws of electrolysis to find the mass deposited, the time or current needed to deposit a target mass, or the moles of electrons transferred, covering the three questions students, hobbyists, and process engineers most often need answered.
How the Electrolysis Calculator works
Electrolysis passes a direct current through an electrolyte, driving oxidation at the anode and reduction at the cathode. Michael Faraday's two laws describe the quantitative relationship: the mass of substance deposited or liberated is directly proportional to the total electric charge passed (first law), and for a fixed charge, the mass is proportional to the substance's molar mass divided by the number of electrons each ion needs to gain or lose (second law).
The calculator implements this in three steps. First, it finds the total charge Q = I·t from the current and time. Second, it converts that charge into moles of electrons by dividing by the Faraday constant, F = 96,485 C/mol — the charge carried by one mole of electrons. Third, it converts moles of electrons into mass using the stoichiometry of the half-reaction: mass = Q·M/(n·F), where M is the molar mass of the deposited substance and n is the number of electrons transferred per ion.
Inputs and what they mean
Current (I), in amps, is the rate of charge flow through the cell — set by the power supply. Time (t), in seconds, is how long the current runs. Molar mass (M), in g/mol, is the molar mass of the element or compound being deposited (for example, 63.55 g/mol for copper, 107.87 g/mol for silver). Electrons transferred (n) comes from the balanced half-reaction — it's 1 for Ag⁺ + e⁻ → Ag, 2 for Cu²⁺ + 2e⁻ → Cu, and 3 for Al³⁺ + 3e⁻ → Al. Getting n wrong is the most common source of error: a higher n means more charge is needed to deposit the same mass, since each ion requires more electrons to reduce.
Limits and edge cases
This calculator assumes 100% current (Faradaic) efficiency — every electron that flows is used for the intended reaction. In practice, real electroplating baths often run at 90–98% efficiency because some current is lost to competing reactions, such as hydrogen gas evolution at the cathode; multiply the calculated mass by the efficiency factor to get a real-world estimate. The formula also assumes a single, well-defined half-reaction with a fixed n — if the deposited species can exist at more than one oxidation state (like copper depositing as Cu⁺ instead of Cu²⁺ under some conditions), confirm which half-reaction applies before trusting the result. Finally, n must be a nonzero integer count of electrons per formula unit — the calculator will not accept n = 0.