According to the Nautical Almanac...

The solar semidiameter will be 15.8', and the radius of the lunar disc will be 14.7'.

So if you are located in the center of the path of totality, the ring around the moon will be 1.1 minutes of arc thick.

I've never seen a total solar eclipse, or an annular one like this, but I have witnessed several partial eclipses (where the moon gives the sun a glancing blow). Even when you know exactly what is going on, it is a very spooky experience. If you're aywhere within driving distance from the path of totality, its worth taking the day off to go see it.

Follow the recommended precautions to protect your eyes. This WILL blind you if you're not careful.