It depends. The larger the diameter, the shorter it can be for the same tune.
If you can, download the free sonosub software and play around with different diameters and lengths. If you change any parameters like port size/length or sonotube diameter length it will show you what the tuning is. You can also go the other way and tell it what tune you want and it can show you what
size/length ports/tube to use. It has a library of drivers too. Probably not as extensive as winisd or bass box but you can enter TS parameters if you want.
Free speaker design software allows easy selection of tube and port size to attain desired tuning frequency
www.subwoofer-builder.com