One centimetre here and there is really not inconsequential, use an electric measuring tool to be safe. There's no cord to restrict you, just make sure you've charged the battery.
From Amazon
Bosch Professional Laser Level GLL 2-10 (red laserLaser, Working Range: up to 10 m, 3x Batteries AA, Pouch)
Conrad Electronic
Bosch Professional GLL 2-10 Multi-line laser Self-levelling, Incl. bag Range (max.): 10 m
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