Choosing the wrong wire size is one of the most common causes of overheating, tripping and electrical fires at home. This guide explains which wire size to use for lights, fans, sockets, AC and geyser, with a ready chart, a simple load calculation and the checks to make before you buy.
Sources: IS 694 (PVC insulated cables up to 1100 V); manufacturer current-rating charts; common Indian residential wiring practice. Final sizing must be done by a licensed electrician.
WHAT THIS GUIDE COVERS
- Why Wire Size Matters
- Wire Size Chart for House Wiring
- Which Wire for Which Appliance
- How to Calculate Wire Size from Load
- Long Runs and Voltage Drop
- Copper vs Aluminium, and FR vs FRLS Wires
- Colour Code and Earthing
- Buying Checklist for House Wires
Most houses in India are wired with four or five wire sizes: 1 sq mm, 1.5 sq mm, 2.5 sq mm, 4 sq mm and 6 sq mm or more for the main line. The question is not which size is “best”, but which size suits each circuit, based on the load it carries and the MCB protecting it.
Undersized wire heats up under load, damages insulation over time and can cause fires. Oversizing everything adds cost without much benefit. The right answer is a simple match between load, wire size and MCB, which this guide walks through.
1. Why Wire Size Matters
Wire size refers to the cross-sectional area of the copper conductor, measured in square millimetres (sq mm). A bigger area carries more current safely. Every wire has a current-carrying capacity; if the current regularly exceeds it, the wire heats up.
The MCB (miniature circuit breaker) on each circuit protects the wire. The basic rule is simple: the MCB rating should not be higher than what the wire can safely carry. A 1.5 sq mm wire on a 32 A MCB is dangerous, because the wire will overheat long before the MCB trips.
2. Wire Size Chart for House Wiring
| Wire size (copper) | Typical current capacity* | Common MCB | Typical use at home |
|---|---|---|---|
| 1 sq mm | ~10 A | 6 A | Light points, fan points on short runs, signal and bell wiring |
| 1.5 sq mm | ~13 – 15 A | 6 – 10 A | Lighting and fan circuits; safer choice for longer runs |
| 2.5 sq mm | ~18 – 20 A | 16 A | Power sockets, fridge, washing machine, microwave |
| 4 sq mm | ~24 – 27 A | 20 A | Split AC, geyser, induction cooktop (dedicated circuit) |
| 6 sq mm | ~31 – 34 A | 25 – 32 A | Sub-main lines, larger ACs on long runs |
| 10 sq mm | ~42 – 46 A | As per load | Main line from meter to distribution board (larger homes) |
*Indicative values for single-core PVC-insulated copper wires run in conduit. Actual ratings differ by brand, insulation type, number of wires in a conduit and ambient temperature. Always check the manufacturer’s chart and follow your electrician’s design.
3. Which Wire for Which Appliance
| Point / appliance | Recommended wire | Notes |
|---|---|---|
| Lights and LED fittings | 1 – 1.5 sq mm | 1.5 sq mm preferred for long runs and many points on one circuit |
| Ceiling fans | 1 – 1.5 sq mm | Usually on the lighting circuit |
| 6 A / 16 A sockets (TV, fridge, washing machine) | 2.5 sq mm | Standard for power socket circuits on 16 A MCB |
| 1 – 1.5 ton split AC | 4 sq mm | Dedicated circuit; 2.5 sq mm only for small, short runs as per electrician |
| 2 ton AC | 4 – 6 sq mm | 6 sq mm for long runs |
| Geyser (2 – 3 kW) | 4 sq mm | Dedicated circuit with 20 A MCB |
| Induction cooktop / oven | 4 sq mm | Dedicated circuit |
| Main line (meter to DB) | 6 – 10 sq mm | Depends on sanctioned load; follow DISCOM and electrician guidance |
4. How to Calculate Wire Size from Load
Add up the wattage of everything that can run at the same time on a circuit, work out the current, then pick a wire whose capacity is comfortably above it, with an MCB that matches the wire.
WORKED MODEL (ILLUSTRATIVE) — SIZING FOUR CIRCUITS IN A 2BHK
Illustrative example with typical appliance ratings. Actual wattage depends on the appliance model. Circuit design should be done by a licensed electrician.
5. Long Runs and Voltage Drop
The longer the wire, the more voltage is lost along it. On long runs, such as an AC on the top floor fed from a ground-floor distribution board, the appliance may get noticeably lower voltage, run hotter and work less efficiently.
As a practical rule, move one size up for unusually long runs: for example, 6 sq mm instead of 4 sq mm for an AC circuit that runs well beyond a typical room-to-board distance. Your electrician can calculate the exact voltage drop for the run length.
6. Copper vs Aluminium, and FR vs FRLS Wires
Copper vs aluminium
Copper is the standard for house wiring because it carries more current for the same size, is more flexible and makes more reliable connections. Aluminium needs a larger size for the same load and is mainly used for service lines and larger cables. Read more in copper vs aluminium wires.
Insulation types
| Type | What it means | Where it fits |
|---|---|---|
| FR | Flame retardant PVC; resists spreading fire | Standard house wiring |
| FRLS | Flame retardant, low smoke | Apartments, offices, places where smoke is a risk |
| HFFR / ZHFR | Halogen-free; very low toxic smoke | Hospitals, high-rise buildings, premium projects |
See different types of electrical wires for a detailed comparison.
7. Colour Code and Earthing
Using a consistent colour code makes wiring safer to maintain. In Indian homes, red is commonly used for phase, black for neutral and green (or green-yellow) for earth; yellow and blue are used for the other phases in three-phase wiring.
The earth wire should not be undersized. For socket and appliance circuits, use an earth wire of a suitable size as advised by your electrician, and connect every metal-bodied appliance and three-pin socket to earth.
⚠ COMMON HOUSE WIRING MISTAKES
- Using 1.5 sq mm wire for AC or geyser circuits.
- Putting a higher MCB on a circuit than the wire can safely carry.
- Running too many wires in one conduit, which reduces each wire’s safe capacity.
- Mixing wire brands or sizes within the same circuit.
- Buying non-ISI or unbranded wires to save money.
- Skipping the earth wire on socket circuits.
8. Buying Checklist for House Wires
ISI mark and standard
Buy only ISI-marked wires conforming to IS 694. Check the BIS licence number printed on the coil and the wire.
Full 90 m length and correct size
Standard coils are 90 m. Check that the length and size printed on the wire match the label, and ask the dealer for a weight or resistance check if you are unsure.
Copper quality
Good wires use bright, multi-strand electrolytic copper. Dull or very thin strands can be a sign of poor quality.
Insulation type
Choose FR at minimum, and FRLS or halogen-free for apartments and commercial spaces.
Plan quantities by size
List the number of coils needed in each size and colour before buying, so the whole job is done with one brand and batch. Compare leading brands in our list of top wire companies in India.
KEY TAKEAWAYS
- 1 to 1.5 sq mm for lights and fans; 2.5 sq mm for sockets; 4 sq mm for AC and geyser.
- The MCB must never be rated higher than what the wire can safely carry.
- Calculate current as watts divided by 230 V, and size up for heavy appliances.
- Move one size up for long runs to limit voltage drop.
- Use ISI-marked copper wires; FRLS or halogen-free for apartments.
- Final circuit design should be done by a licensed electrician.
Get a Bulk Quote for House Wires
✓ ISI-marked wires from leading brands ✓ All sizes, FR / FRLS / HFFR ✓ Bulk supply for builders and contractors
Disclaimer: Current ratings and recommendations in this article are indicative and for general information only. They vary by manufacturer, installation method and site conditions. Electrical installations must be designed and carried out by a licensed electrician in line with applicable Indian standards and local regulations. Contact Headsup B2B for current product availability and quotes.
