It's never a good idea to guess with measurements, that's what measuring tools are for. No need to look for a power outlet, since it runs on batteries. Just get at it!
From ManoMano
Gcl 2-15 + RM1 aa batteries Cross line laser - Bosch
Buyaparcel
Bosch GCL2000 Self Leveling Combi Cross Line Laser Level + RM1 Bracket + Bag
This product is also available at 5 unverified stores.