Electrolysis Calculator
Estimate electric charge and the ideal mass deposited, dissolved, or produced during electrolysis using Faraday's first law.
Electrolysis inputs
Live result
Material comparison at the same charge
| Material | Z (mg/C) | Ideal mass | Relative to selected |
|---|
The comparison holds charge constant and applies each preset electrochemical equivalent. It is a calculation table, not a prediction of practical yield.
How to use the electrolysis calculator
What this calculator does
This calculator applies Faraday's first law to estimate the ideal mass of a substance deposited, dissolved, or generated when a known direct current flows for a known time. It calculates electric charge from current and time, then multiplies that charge by the selected electrochemical equivalent. The result is a theoretical quantity under the simplifying assumption of 100% current efficiency. It does not account for side reactions, gas leakage, electrode passivation, concentration limits, temperature effects, changing resistance, or other losses found in a real cell.
When to use it
Use it to estimate metal plating mass, compare materials under the same charge, check classroom or laboratory calculations, or approximate hydrogen and oxygen production before applying a measured efficiency factor. The underlying relation follows the electrochemical form of Faraday's laws; the IUPAC Gold Book entry for Faraday's laws provides authoritative terminology.
How to calculate
- The calculator opens with a complete demonstration: Copper (Cu), 2 A, and 60 minutes. Its results and a validated example XLSX workbook are immediately available.
- Choose an Element or product. The calculator loads its preset electrochemical equivalent. Choose Custom to enter your own value.
- Enter Current (I) in amperes and Time (t), then choose seconds, minutes, or hours. Results update as you type.
- Read Ideal mass (m), Charge (Q), Electron amount, and the normalized current and elapsed time. The comparison table shows what the same charge would produce for several presets.
- Select Download Excel to export the current typed inputs, results, comparison rows, and notes. Reset clears the demonstration data and may disable the export until you enter a complete valid state again.
Input guide
Element or product is required and selects a preset species. Each preset uses a specific assumed ionic valence, so iron is shown as Fe²⁺ and the gases as H₂ and O₂. A common mistake is choosing the right element but the wrong ionic charge for the actual half-reaction. Electrochemical equivalent (Z) is required and expressed in milligrams per coulomb. Presets lock this field; Custom unlocks it. Enter a positive decimal such as 0.5000 mg/C. Do not paste units, commas used as decimal marks, or scientific notation. Current (I) is a required positive decimal in amperes; 2 A is the startup example. Higher current increases charge and mass in direct proportion. Time (t) is a required positive decimal, paired with the Time unit selector. The sample uses 60 minutes, equivalent to 3,600 seconds. Switching the unit converts the entered duration so the physical time stays unchanged. Zero, negatives, unsupported symbols, and numbers large enough to overflow are rejected.
Output guide
Ideal mass (m) is the theoretical product mass, displayed in a convenient mass unit; it is an estimate rather than a guaranteed yield. Charge (Q) is the exact identity I × t in coulombs. Electron amount converts charge to moles of electrons using the Faraday constant and helps connect electrical charge to reaction stoichiometry. Current repeats the validated amperage, while Elapsed time shows the normalized duration in seconds. The formula line exposes the multiplication used. The material comparison table reports each preset Z, the ideal mass at the same charge, and its ratio to the selected material; a ratio above 1 means more mass per coulomb, not necessarily better efficiency or economics.
Worked example
For the startup values, 2 A flows for 60 minutes. First convert time: 60 min × 60 s/min = 3,600 s. Charge is Q = I × t = 2 A × 3,600 s = 7,200 C. Copper's preset electrochemical equivalent is 0.0003294 mg/C, equivalent to 3.294 × 10⁻⁷ kg/C. Therefore m = Z × Q = 0.0003294 mg/C × 7,200 C = 2.37168 mg, displayed as 2.372 mg. The charge also corresponds to about 0.07462 mol of electrons using the NIST value of the Faraday constant. Practical deposited mass is often lower; if measured current efficiency were 90%, multiply the ideal mass by 0.90.
Formula, assumptions, and practical interpretation
Q = I × t and m = Z × Q
Electric current is charge flow per unit time, so one ampere equals one coulomb per second. The BIPM SI Brochure is the definitive reference for SI unit definitions. The electrochemical equivalent Z packages molar mass, electron count, and the Faraday constant into a convenient mass-per-charge factor. Equivalently, the ideal mass can be calculated as m = MIt/(nF), where M is molar mass, n is the number of electrons transferred per formula unit, and F is the Faraday constant.
The largest practical limitation is current efficiency. If only a fraction η of the supplied current drives the desired half-reaction, use mactual ≈ ηmideal. For gas production, collection efficiency and ambient conditions add further uncertainty. For plating, surface preparation, current density, bath composition, and agitation affect deposit quality even when total charge is correct. The U.S. Department of Energy overview of hydrogen production by electrolysis explains the broader process and system context.