The specific bulb you need will be clearly listed on the product page of your particular chandelier. Please make sure you buy the correct bulb.
There are 4 standard types:
E14 – 14mm diameter, Small Edison Screw Cap (SES)
E27 – 27mm diameter, Edison Screw Cap (ES)
B15 – 15mm diameter, Small Bayonet Cap (SBC)
B22 – 22mm diameter, Bayonet Cap (BC)