I just took a tape measure to mine ...
The waistband is 34 inches unstretched, therefore I stretch it by an inch or so, which is ok - it leaves a mark round my waist but does not feel like it is strangling it!
Pulling very hard on the waistband, it is possible to stretch it to 41 inches, but no way would that have suited me when I was that size!
Below 34 inches, you would need to use the integrated belt to keep the shorts up.