One centimetre here and there is really not inconsequential, use an electric measuring tool to be safe. No need to look for a power outlet, since it runs on batteries. Just get at it!
From Amazon
Bosch Professional 12V System Laser Level GLL 3-80 C (Without Battery and Charger, red Laser, w/app Function, Mount, Working Range: 30m, in L-BOXX)
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