CaLibration L

This is my go to shape for calibrating steps per mm.

Only used for X and Y with the corner marked with an X and a / for x and y.
print at 100% scale and you can use the depth probe on a caliper to find the actual size of each axis. Using depth probe instead of inside or outside calipers means the ooze and expansion doesn't affect the measurement since your measuring faces with the same normal direction.