How to properly measure for a new desk top.

Just a little quip I'm writing about today on the bonehead mistake I made.  Perhaps someone else can learn from my errors! So. Drexel Campaign Desk. Suh-weet! 
Friend found it in Vegas and hauled it back for me. Thought it was a good deal until I 
got a close look at it. 

You're probably thinking what's the big deal?? A little veneer action. So what.  Um, no. I forgot to snap pics before hub and I got all the glue and clamps on. 

But you can probably get the gist of just how tore up this baby was. 

 It was lopsided because it was out of the grooves. Now the drawers will close well. 

 Ok. This post isn't about the desk so much as what I did wrong while measuring for a new top. Below is the laminate crap top that it came with. I like real wood.  I have done this on a previous mid century desk using cherry HERE.   

This desk is made of oak. So I went to the lumberyard at bought some white oak planks. As you can see the desk top is 46". So I measured the planks at 46", thinking it would work. 

 Uh, no. Just a tad off.  What the heck??!!! 

 So. What I SHOULD have done, and what I did with the last plank before I cut, was to measure it from the desk itself, not the MDF top. I guess the other top had a beveled edge that made up that 1/2" difference. Oh well. Lesson learned. Went back to the lumberyard and bought 4 more pieces. This time had the old man do it.   Sigh. 

 Stay tuned for the finished product. I plan on doing a weathered gray ceruse on this top.