How many metres of string lights does your balcony need? Drape them and see

Balcony width

Balcony depth

Distance to the socket

Hook spacing

Droop per swag

0 m

cable to buy, at least

Metric measurements. The drawing is to scale for the width and depth you set. The result is a minimum: lit length plus the cable to your socket plus 10% for knots, hooks and corners.