What is the thickness of a steel bar with holes?

[GulfOnBoard]

TL;DR Summary

Calculation of thickness.

I’m trying to calculate the thickness of a steel bar with holes. It’s hard to describe so here’s a picture Imgur: The magic of the Internet (the white circles are 10mm holes and the dark grey area are 2mm steel wallthickness).

If the holes would be horizontal inline to each other with 2mm steel between them and also 2mm steel at the outerwalls, the overall thickness would be 26mm, but with the pattern in the picture the thickness will be less, but exactly how much less?

 

[berkeman]

Why does the "bar" have dimple features? Are the holes formed by drilling or by punching? If by drilling, why would a "bar" be deformed?

 

[berkeman]

Or is your question just one of how to calculate the distances using trigonometry? We can help with that if you haven't had trig yet. What is the application?

 

[mfb]

This doesn't need trigonometry. Draw a triangle between the centers of three adjacent circles. It is an equilateral triangle, you know its side lengths, and you can find its height with the usual formula (or Pythagoras if you want to derive that formula). Add the known distances to the left/right edges and you have the total width.