Yes, you can take a laser tape measure on a plane, but it should be packed in your carry-on luggage. Most laser tape measures are considered tools and are generally allowed, as they do not pose a security threat. However, it's always best to check the specific regulations of the airline and the Transportation Security Administration (TSA) or equivalent authorities in your country before traveling.
A tape measure.
You take a ruler or tape measure and measure the dimensions you need.
cm,m If you're measuring something not really large, then use a tape measure. If it's something large, use a laser. If you don't have a laser, then set aside adequate time and get friends to help with the task.
Lengths - in units that are marked on the tape measure.
-- ruler -- tape measure -- meter stick -- yardstick -- car's odometer -- laser rangefinder -- split-image rangefinder