The regular calibration cubes may not be the best thing to calibrate a printer. Edges and particularly the bottoms can be distorted. If you measure the overall size this can yield a slightly inaccurate measure of scale.
This thing has lines and diamonds on both horizontal and vertical faces at 25mm spacing.

I have uploaded 3 variants of this thing. The complete corner will give a little bit more information but the choice is yours.

I have other test patterns here -
http://www.thingiverse.com/thing:23965

Ideally you should slice with the layer height being a factor of the Z distance you are going to measure.
For example .4mm slices requires 62.5 layers to build 25mm in height.
But 50 mm is 125 full layers.
.25mm should be good except the .4mm lines of the vertical faces might slice strangely.
However there should be enough marks visible to get your calipers into.