House-Wire Size Calculator
Estimate the right copper wire size for any home or building circuit — and the matching APAR wire. Based on Indian practice (IS 732 / IS 694), 230 V single-phase and 415 V three-phase.
⚠️ Guidance only. Assumes copper conductors in conduit at normal ambient temperature, a 1.25× design margin and your selected voltage-drop limit. Actual sizing depends on installation method, grouping, ambient temperature and local regulations. Always have the final design confirmed by a licensed electrician.
How do you calculate wire size?
The methodThe “size” of a wire is its cross-sectional area — the area of copper at a cut end. A larger area carries more current with less resistance, much like a wider pipe carries more water with less pressure loss. Two laws of physics set the minimum size.
Combining them — and allowing for the current’s return path — gives the minimum area:
In practice the calculator uses standard mV/A/m figures for each size (which bake in resistivity, the return path and real construction), applies a 1.25× design margin, finds the smallest size whose rating covers the load, checks voltage drop against your limit, and finally coordinates the size with the MCB — the two safety checks a bare chart skips.
A worked example
Step by stepReference chart
Copper, in conduit| Size (sq mm) | Current rating (A) | Voltage drop (mV/A/m) |
|---|---|---|
| 1.0 | 11 | 44 |
| 1.5 | 14 | 29 |
| 2.5 | 19 | 18 |
| 4 | 26 | 11 |
| 6 | 34 | 7.3 |
| 10 | 46 | 4.4 |
| 16 | 61 | 2.8 |
Frequently asked questions
Good to knowFor home-wiring applications, explore these ranges. Ask our team to confirm a suitable product for your application.
