Snip from the 5pm Public Advisory:

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 70 MILES FROM THE
CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 175
MILES.

This means that the hurricane force wind field is approximately 140 across and the tropical storm force wind field is approximately 350 miles across. Since the storm is very symetrical, this is probably pretty darn accurate. Normally the bulk of the wind field is not even on all sides of the storm.

Another poster asked about size comparison to Katrina. Based on a quick visual peak at the maps, it appears that Katrina's wind field was slightly larger than Rita when comparing the advisories issued when the storms were first classified as category 5. Certainly, the hurricane force wind field was larger for Katrina at this point. You can see the archived maps for Katrina at www.skeetobiteweather.com, look in the lower right of the home page for archived storm links.

If I get a chance, I'll dig through the database and do a comparison to give you the exact numbers.