What is it?
The Wire Size Calculator suggests the cable size to use for a load and a distance. It shows the smallest size that keeps the voltage drop low, how much current that cable can carry, and the voltage drop with it.
Who is it for?
Electricians, homeowners planning wiring, solar installers and engineering students.
How to use it
Choose the Supply and Wire metal. Enter the Supply voltage, Load current, Cable length (one way) and the Voltage drop allowed (3% or 5% is typical). The answer appears as you type; there is no Calculate button. Tap Copy result to copy it, or Share on WhatsApp to send it.
Two checks, both must pass
- Current capacity: the cable must carry the current without overheating. This depends on insulation, how it is laid (conduit, wall, air) and how many cables share a conduit.
- Voltage drop: long runs need thicker cable even for small loads.
Typical home sizes (copper, India)
- Lighting circuits: 1–1.5 mm². Power sockets: 2.5 mm². AC and geyser points: 4 mm². Main from the meter: 6–10 mm² or more, depending on load.
- Aluminium needs about 1.6 times the copper size for the same current.
The “can carry” figure is a typical value; manufacturers’ tables and local codes give the exact rating for your installation.
Electrical work can kill. Use these numbers for planning and learning; have a licensed electrician do and check any wiring, following your local wiring rules.
Errors and how to fix them
- “That needs more than 300 mm²: use parallel cables or ask an electrician”
Open the tool: Wire Size Calculator
Still stuck?
Contact support. Tell us which tool or page you were using, what you tapped, what you saw, and your phone or computer and browser (for example: Android phone, Chrome). We reply by email.
Questions, or an error not listed here?
Tell us in the comments: what you were doing, the exact message you saw, and your device and browser. We read every comment and add new fixes to this article.