Formula for power source vs led strips

[plant57va]

I recently pur chased a few waterproof light strips, planning on using them more for viewing than as a light source for growing plants.
I want to know if there is a computation for knowing what power source to use for multiplease lights.

They are:
20" long, SMD 5050. 30 led per strip
12v dc, 6 watt, cold white (6500-7000k) 120°
Protectivery rating IP67

So if I am linking up several to one source, what size do I need?
Thanks...... I seem a bit electrical challenged on this one

[Cristy Keister]

PVAS had a speaker on those LEDs. Here are pics I took showing the power consumption.

2017-02-02 13.13.47.jpg (951.58 KiB) Viewed 1252 times

2017-02-02 13.16.28.jpg (869.11 KiB) Viewed 1252 times