How high do you build your windows?

Sit in a chair, get at a comfortable height lean forward and drop a tape measure to the ground.

I make mine38.5" but 39" is more or les standard, an adjustable chair make things very nice. I also like to put a 5" shelve in mine.

The above is good advice IF you are shooting level or fairly level. Average height 38" to 40 from floor. But then young or older person wants lower. Also tower blind may need to be lot lower for downward shots or higher for uphill shots. Some add flat 1 x 6 at window level to raise and steady the gun barrel. Then I'm crazy enough and make my blinds out of privacy fencing and window will have stair step hole, one slat 38', next one 39, and next 40". Have various terrain and various ages of family using em. Then you can also have an adjustable chair.
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90% Texan

39" is where my shelf is and if you put it there and then get an adjustable office chair you can lower or raise yourself to be just about right

My son is wanting to make some money and I have a half built deer stand. So Im letting him (He's 10yo) finish the stand and he's going to sell it to make some money for camp. So I was just wandering a good average height. I think Ill go with 39in Thanks guys!!

+1 on this one... Good fit for me but a little tall for the kids.

+2 i am puttin an 1x8 in for the shelf in all windows works great for puttin a sand bag on for a rock solid rest

39" from inside floor up......