Determining the capacity requirement of the DC power supply for your LED strip lights is simple.
Just take the length of LED flexible strip light you’ll be using ) and multiply that length by the number of watts that type of LED flexible strip light consumes per foot or metre (there are 3.28 feet in a metre). The power consumption per metre is in the description and specifications of the web page for each model of LED flexible strip light.
eg. 5 metres of LED flexible strip light x 9 watts per metre = 45 watts of power supply capacity required per reel. So you’d choose a 60 watt power supply.