SIMPLE MATH HELP - how big a monitor i can have

[The Torrent]

i cant do this simple math. must be too late.

I have a 35inch curved monitor ultrawide infront of me. i want to imitate this setup of reddit:

 

a comfortable height im good with monitor to be infront of me is 20cm up from the desk. heres a paint drawing.

after doing ultrawide math assuming 21:9 screen so 20inches/21 x 16.

so root (20^2 + (20/21 x 16)^) = just over 25. ok. i can have a 25 inch monitor. after measuring that 20 inches is about 51cm.

so i look at the monitor sheet. (lg 25inch monitor)

those aint 5cm boarders on each side. tf.

if i move my screen up 60cm thats just toooooo high. thats 10cm over my incorrect dodgy math.

 

 

help

 

[minibois]

A 21:9 25" monitor would be 585.07mm x 246.82mm, not counting the borders.

So that means and 12mm border on either side. That seems pretty believable, considering there is a plastic border and then another inner border to LG monitor.