I'm going to try to re-do my dining room floor using the IKEA Tundra laminates. I've never done this before, so I'm going into this completely blind. :) I heard that I might need to cut the first plank so that it is equal to the last plank, otherwise I might end up with a tiny sliver of plank for the last plank, which I don't want. Can I please get some help in calculating this?

My dining room has 3 medium windows on the left angled wall.
One other wall is the longest wall.
Opposite that, instead of a wall, is black railings a little more than halfway the length, until it hits the floor-to-ceiling post.

TUNDRA PLANK INFORMATION:

LENGTH: 138 cm
WIDTH: 19.3 cm

I've calculated it like this:

*87cm/19.3cm = 4.5
*19.3cm + 4.5 / 2 = 11.9 cm

So I think that the very first plank and the very last plank need to be 11.9 cm in width. So I guess I cut 7.4 cm off the tongue side of the first plank (since the cut-off tongue side is the one going into the wall)?

Is that at all correct (LOL)?

Also, did I get the plank direction correct? I heard you should put the planks in a way that follows the longest wall.

I'm also a little intimidated by the floor-to-ceiling post and the railings, and how they affect the laminates. So far I'm just planning on cutting the planks until they fit against the post.

Thanks for any help!

CRAPPY DRAWING OF DINING ROOM (NOT TO SCALE):