Question: I'm replacing the wiring from a vintage chandelier and need to know what gauge wire to use. There are five lights on it. This is for the fixture only!

Answer: 
18g stranded wire is [quite common on arms](http://www.thisoldhouse.com/toh/photos/0,,20267510_20599803,00.html)
14g stranded is often used to join the 18g arm strands, and to tie into the ceiling.

This applies to North America and normal chandeliers with relatively low (<50 each) wattage bulbs.
If you're in the US, NEC likely applies. Article 402 covers fixture wires, and explains what types and sizes are allowed. 

Type
====

Table 402.3 lists the types of wires allowed to be used as fixture wires. If you're going to rewire the fixture, you'll have to use a type of wire listed in this table.

* FFH-2
* HF, HFF
* KF-1, KF-2, KFF-1, KFF-2
* PAF, PAFF
* PF, PFF
* PGF, PGFF
* PTF, PTFF
* RFH-1, RFH-2, RFHH-2, RFHH-3
* SF-1, SF-2, SFF-1, SFF-2
* TF, TFF
* TFN, TFFN
* XF, XFF
* ZF
* ZFF
* ZHF

Size
====

Table 402.5 lists the allowable ampacity for different sizes of wire. You'll want to use a wire that's sized properly for the load you'll be serving. In most cases, the maximum bulb size you'll have to account for is 100 Watt. Which means you'll likely only be looking at about 833 mA (100 Watts/120 Volts), so you can probably get away with 18 AWG wire.

> 
> ![Table 402.5](https://i.stack.imgur.com/tkY7x.png)
> 
> 
> 

402.6 says that fixture wires cannot be smaller than 18 AWG, so you'll have to use at least that size wire.

Overcurrent Protection
======================

402.12 points to 240.5 for overcurrent protection of fixture wires, which tells you what size overcurrent is required for different sized wires. 240.5(B)(2) lists the size and length of fixture wires, when connected to circuits with various sizes of overcurrent protection.

> 
> National Electrical Code 2014
> =============================
> 
> 
> Article 240 Overcurrent Protection
> ----------------------------------
> 
> 
> ### I. General
> 
> 
> **240.5 Protection of Flexible Cords, Flexible Cables, and Fixture Wires.**
> 
> 
> **(B) Branch-Circuit Overcurrent Device.**
> 
> 
> **(2) Fixture Wire.** Fixture wire shall be permitted to be
>  tapped to the branch-circuit conductor of a branch circuit in
>  accordance with the following:
> 
> 
> (1) 20-ampere circuits — 18 AWG, up to 15 m (50 ft) of run length  
> 
>  (2) 20-ampere circuits — 16 AWG, up to 30 m (100 ft) of run length  
> 
>  (3) 20-ampere circuits — 14 AWG and larger  
> 
>  (4) 30-ampere circuits — 14 AWG and larger  
> 
>  (5) 40-ampere circuits — 12 AWG and larger  
> 
>  (6) 50-ampere circuits — 12 AWG and larger 
> 
> 
> 

Conduit/Tube Fill
=================

You may also have to refer to Table 1 of Chapter 9, to determine the maximum number of wires that can be in a conduit or tube.