You can make it whatever size you want!
A queen size mattress is a standard size for the top ONLY.
The height of the mattress can vary from thin to those jumbo extra deep mattresses.
Then it depends on what frame you are setting the mattress on/in.
Consider whether you want it tucked around the pillows?
Or tucked in at the foot of the bed?
And how much you want your quilt to hang down .... floor to floor or just over the top of the bed, etc.
So many variables ... that you really cannot stick to a standard size.
For example ... I have an antique double bed.
100" square is none too large ... and yet many would call that a king quilt!