Onehundred and fiftyfour miles of river from Cricklade to London Bridge, of course the river goes down stream below London Bridge but I have not got this information to hand at the time of writing this introduction to the river, but should you be interested there are photos on the other Thames pages.
As you can see from the map the river is a most meandering water course, so much so that the distance between some towns is much shorter by road than water.
This page as most on the site is heavily illustrated and takes time to download, so be patient and enjoy it when you get there.