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Electrolysis Calculator

Chemistry

Calculate mass deposited or gas produced during electrolysis using Faraday's law: m = MIt/nF. Select element or enter custom molar mass, current, and time.

Reviewed by the thecalcu.com team · Last updated November 10, 2025

63.55 g/mol
g/mol
2
2 A
A
30 min
min

Mass Deposited

1.185
Moles Produced
0.019
Total Charge
3,600
Volume at STP (gas)
0

This calculator computes your Mass Deposited, Moles Produced, Total Charge, Volume at STP (gas) from the values you enter.

Inputs
SubstanceMolar Mass (custom only)Electrons per Formula Unit (custom only)CurrentTime
Outputs
Mass DepositedMoles ProducedTotal ChargeVolume at STP (gas)

What is a Electrolysis?

The Electrolysis Calculator determines the mass of metal deposited (or gas produced) during electrolysis using Faraday's law: m = MIt/(nF), where M is molar mass, I is current in amperes, t is time in seconds, n is the number of electrons transferred per formula unit, and F = 96,485 C/mol. Select a substance from the preset list (copper, silver, gold, zinc, nickel, iron, aluminium, H₂, O₂, Cl₂) or enter custom values.

Faraday's law is exact for ideal electrolysis: every electron that flows deposits or dissolves one (1/n)th of a mole of the target species. The law connects the macroscopic (current in amperes, time in seconds, mass in grams) with the molecular scale (Avogadro's number, elemental charge). This calculator implements both Faraday's laws, mass proportional to charge, and mass proportional to equivalent weight, in one unified formula.

For the reverse calculation (finding the current or time needed to deposit a target mass), rearrange: I = mF×n/(M×t) or t = mF×n/(M×I). The Cell EMF Calculator provides the thermodynamic context (minimum voltage needed) and the Nernst Equation Calculator accounts for concentration effects on the required voltage.

Why Use an Electrolysis Calculator?

The unit conversion in Faraday's law is the main source of error: time must be in seconds (not minutes), current in amperes, and F = 96,485 C/mol (not 96,000 or 100,000). Students often forget to convert minutes to seconds, leading to answers that are 60× too small. This calculator takes time in minutes and converts internally.

For JEE and NEET, Faraday's law problems appear in numerical form (mass deposited, time needed, current efficiency) and qualitative form (comparing mass of different metals deposited by the same charge). The preset substance list covers the most common exam elements.

Who Should Use This Calculator?

Class 12 and undergraduate chemistry students covering electrochemistry (NCERT Chapter 3): Faraday's laws, electrolysis, and electrolytic cells are standard CBSE, JEE, and NEET examination topics.

Jewellery and metal finishing engineers computing electroplating time and current settings to achieve target coating thicknesses of gold, silver, nickel, and chrome on substrates.

Industrial electrochemists at aluminium smelters, copper refineries, and chlor-alkali plants calculating theoretical production rates from electricity input and current efficiency.

Chemical engineering students working on electrochemical reactor design, connecting current density (A/m²), electrode area, and production rate through Faraday's law.

What Insights Does the Electrolysis Calculator Give You?

Mass Deposited (g) is the primary output, the theoretical mass of metal electrodeposited or gas electrolytically produced, assuming 100% current efficiency. For gases, this is the mass of the molecular species (H₂, O₂, Cl₂).

Moles Produced is the mass in moles, useful for stoichiometric calculations, such as how much H₂ is produced alongside NaOH in the chlor-alkali process, or comparing moles of two metals deposited by the same charge.

Total Charge (C) = I × t, the total coulombs passed. Dividing by Faraday's constant (96,485 C/mol) gives moles of electrons, the fundamental electrochemical quantity.

Volume at STP (L) appears for gas products (H₂, O₂, Cl₂): moles × 22.414 L/mol. A useful check: water electrolysis produces H₂ and O₂ in a 2:1 volume ratio at any current.

How to use this Electrolysis calculator

  1. Select the Substance from the dropdown. Copper and silver are most common in educational problems; hydrogen and oxygen for water electrolysis.
  2. For Custom substance: enter the Molar Mass (g/mol) and Electrons per Formula Unit (n).
  3. Enter the Current in amperes. Common lab electrolysis: 0.5–5 A. Industrial: 100–500,000 A.
  4. Enter the Time in minutes. The calculator converts to seconds internally (multiply by 60).
  5. Read Mass Deposited and Total Charge, verify with the known electrochemical equivalent for the element.
Show formula & methodology ↓Show less ↑

Formula & Methodology

Faraday's law of electrolysis:

m = M × I × t / (n × F) Q_charge = I × t    (coulombs) moles = Q_charge / (n × F)

Gas volume at STP:

volume_STP = moles × 22.414 L/mol

Worked example, copper electroplating:

Deposit copper from CuSO₄ solution: Cu²⁺ + 2e⁻ → Cu (M = 63.546 g/mol, n = 2). Current I = 2 A, time = 30 minutes = 1800 s.

Q = 2 × 1800 = 3600 C moles Cu = 3600 / (2 × 96485) = 3600 / 192970 = 0.01866 mol mass = 0.01866 × 63.546 = 1.186 g

At 2 A for 30 minutes, 1.19 g of copper is deposited, enough to coat a surface area of about 40 cm² with a 1 μm thick layer (copper density = 8.96 g/cm³). This is the type of calculation jewellery manufacturers and printed circuit board platers perform to set plating parameters.

Frequently Asked Questions

What is electrolysis and how does it work?
Electrolysis is the non-spontaneous decomposition of a substance by passing electrical current through it. An external power supply forces electrons to flow: at the cathode (negative electrode), cations are reduced (gain electrons); at the anode (positive electrode), anions are oxidised (lose electrons). Electrolysis is used to extract metals from ores, electroplate surfaces, produce industrial chemicals (Cl₂, NaOH via the chlor-alkali process), refine metals (electrolytic copper refining), and produce hydrogen by water splitting.
What is Faraday's law of electrolysis?
Faraday's first law: the mass of substance deposited or dissolved is proportional to the total charge passed: m ∝ Q (where Q = I × t, charge in coulombs). Faraday's second law: for the same charge, the masses deposited of different substances are proportional to their equivalent weights (M/n). Combined formula: m = MIt/(nF), where M is molar mass (g/mol), I is current (A), t is time (s), n is the number of electrons per ion, and F = 96,485 C/mol is Faraday's constant.
How do I use the Electrolysis Calculator?
Select the substance being deposited or evolved (copper, silver, gold, zinc, nickel, iron, aluminium, hydrogen gas, oxygen gas, chlorine gas, or custom). Enter the current in amperes and the time in minutes. For custom substances, enter the molar mass and the number of electrons per formula unit. The calculator returns mass deposited (g), moles produced, total charge (C), and volume at STP for gases.
What is Faraday's constant and what does it mean?
Faraday's constant F = 96,485 C/mol is the charge carried by one mole of electrons = N_A × e = 6.022 × 10²³ × 1.602 × 10⁻¹⁹ = 96,485 C. It means that to deposit one mole of a univalent ion (n=1, like Ag⁺ → Ag), you need 96,485 coulombs = 96,485 A·s. For a divalent ion (n=2, like Cu²⁺ → Cu), one mole of metal requires 2 × 96,485 = 192,970 C. For practical current (2 A), one mole of copper takes 192,970/2 = 96,485 seconds ≈ 26.8 hours.
How does current efficiency affect actual mass deposited?
This calculator assumes 100% current efficiency, all charge goes to the desired electrode reaction. In practice, competing reactions (hydrogen evolution, oxygen evolution, side reactions) reduce current efficiency to 70–95% for most industrial processes. Copper electrorefining achieves ~95% efficiency; aluminium smelting ~90%; industrial chlor-alkali ~95%. To account for current efficiency η%: multiply the calculator's mass by η/100. Current efficiency is determined empirically for each specific process.
How is electrolysis used in industrial metal production in India?
India is a major producer of electrolytic metals. HINDALCO and NALCO produce aluminium via Hall-Héroult electrolysis (Al₂O₃ in molten cryolite, E ≈ 4–5 V, ~300–500 kA currents). Copper India (Vedanta) and Hindustan Copper produce electrolytic copper (99.99% pure). Hindustan Zinc uses electrolytic zinc refining. The chlor-alkali industry (Gujarat Alkalies, GACL, DCM Shriram) electrolyses brine to produce Cl₂ and NaOH, essential for India's PVC and chemical industries.
What is electroplating and how is Faraday's law applied to it?
Electroplating deposits a thin metal coating on a substrate for corrosion protection, aesthetics, or wear resistance. The cathode (workpiece) gains metal; the anode (often the plating metal) dissolves. Mass deposited = MIt/(nF). For a gold-plated jewellery piece: plating 2 μm of gold (M = 196.97, n = 3) over an area of 50 cm², density of Au = 19.3 g/cm³: mass = 50 × 0.0002 × 19.3 = 0.193 g. Time at 0.5 A: t = m×n×F/(M×I) = 0.193 × 3 × 96485 / (196.97 × 0.5) = 565 s ≈ 9.4 minutes. The BIS (Bureau of Indian Standards) specifies minimum plating thicknesses for various applications.
What is the chlor-alkali process and what products does it yield?
The chlor-alkali process electrolyses concentrated NaCl brine: Cathode: 2H₂O + 2e⁻ → H₂(g) + 2OH⁻; Anode: 2Cl⁻ → Cl₂(g) + 2e⁻. Products: Cl₂ gas (anode), H₂ gas (cathode), NaOH solution. All three are commercially valuable: Cl₂ for PVC, disinfectants, and solvents; NaOH for aluminium production, paper, soap, and textiles; H₂ for ammonia synthesis. India's chlor-alkali capacity is approximately 4 million tonnes of NaOH per year, supporting the country's chemical industry.
How is electrolysis of water used for hydrogen production?
Water electrolysis: 2H₂O → 2H₂ + O₂ (E°cell = −1.23 V; requires ≥1.23 V external voltage, typically 1.8–2.0 V with overpotentials). Cathode: 2H₂O + 2e⁻ → H₂ + 2OH⁻. Anode: 2OH⁻ → ½O₂ + H₂O + 2e⁻. Per 96,485 C (1 Faraday): 0.5 mol H₂ = 11.2 L at STP at cathode; 0.25 mol O₂ = 5.6 L at anode. India's National Green Hydrogen Mission targets 5 million tonnes per year of green hydrogen (electrolytic, from renewable electricity) by 2030, requiring ~125 GW of electrolysis capacity.
What is the relationship between Faraday's law and the Avogadro number?
Faraday's constant F = N_A × e = (Avogadro number) × (elementary charge). This relationship is how Avogadro's number was originally determined with high precision. By measuring the mass of silver deposited per coulomb (the electrochemical equivalent of silver = M/nF = 107.87/(1 × 96485) = 1.1180 mg/C), and knowing the charge of a single silver ion, N_A = F/e = 96485 / 1.602 × 10⁻¹⁹ = 6.022 × 10²³. Faraday's electrolysis experiments (1833) and Millikan's oil drop experiment (1909) together gave the first precise measurement of N_A.