It's never a good idea to guess with measurements, that's what measuring tools are for. Among the measuring tool's handy features you'll find that it's self leveling.
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Milwaukeee M12 3PL-0C 3 x 360° Cross Line Laser
Tools4trade
Milwaukee M123PL-0C 12V 360° 3-Plane Green Laser with Case - Default
ITS
Milwaukee M12 3PL-0C 12V Green 360° 3 Plane Laser - Body with Case