How to figure out if room is square  install Mohawk engineered flooring
New to remodel thing...
How do I figure out if a room is square? Laying engineered hardwood in LR and into adjoining hall and don't want it out of wack. Thanks. 
Measure the diagonals. If they're the same, then your corners are all 90 degrees. If they're not, then your room is not a rectangle (or square).
When I measure to cut moldings like baseboards and shoe moldings, I stick a carpenter's square in one corner and measure the distance from the end of the square to the other corner, then add the length of the carpenter's square. Do something similar to accurately measure the diagonal between corners. If your diagonals aren't the same, you can use the 3,4,5 rule to find out which corner isn't square. The 3,4,5 rule says that an isosceles triangle with sides of length 3 units, 4 units and 5 units (for the hypotenuese) will form a right angle between the sides of 3 and 4 units. So, measure off 9 feet along one wall from one corner, 12 feet along the adjacent wall from the same corner, and the distance between your marks should be exactly 15 feet. If it isn't, then that corner is out of whack. And, from the length of the diagonal you measure, you can determine what the angle of that corner is here: http://ostermiller.org/calc/triangle.html If you have trouble using that calculator, it may be because the option of selecting the angle units is set to radians instead of degrees. A radian is 360/2pi or about 57 degrees. 
Nestor:
An isosceles triangle is a triangle with (at least) two equal sides. A 3,4,5 triangle obviously doesn't have two equal side. I think you're looking for a right triangle with 3,4,5. Is there a wall between these two areas or are they basically connected like an L? Bob 
When I do flooring that is going down a hallway and into multiple rooms, I always start at a line from the hallway into the other rooms. This is your baseline. Build from there.
The reason I do this is because people walk down hallways and will see that it is not square. Also if there is another room that is going to have the flooring then it will be square to the hallway. I have seen jobs where the homeowner started from an outside wall and was off just a little and when they got to the hallway it was real obvious that they were off. They called me and I told them how to do it from the hallway. They ended up being a little off at the outside wall but it was easy to deal with because there is usually furniture there to hide the slight variation. Not so in a hallway. 
Thanks!
I appreciate the help. Sorry for the delay in answering but remodeling is taking forever!

squared walls?
It is walled off with a 3132" door separating.
Quote:

I think Marvin is on the right track; keep the wood straight to the wall that most people will notice. Any irregularities would then go to the wall is least visible. I bought a laser level that shoots a beam out to help me do this in my hall; I let it run down the floor and was a big help. You can use string as well, I like gadgets and got it cheap on ebay.
http://www.blackanddecker.com/Produc...ProductID=7859 
As much as I hate to agree with Marvin he is on the right track. The hall is the area that will look the most out.
I however will square the hallway up with all rooms and split the differnce if it is do far out of square. Hallways can fool you. they have a tendenecy to not be a straight as they look and the reason is the doorways and a lack of an main bearing wall. I will use the nearest main bearing wall as the guide wall for the hall. 
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