I don't know how much it varies from state to state but it was "within 6 inches" when I took my test many years ago.
18 in
16 inches
6
From the Calfornia DMV web page on parking: When you park alongside a curb on a level street, the front and back wheels must be parallel and within 18 inches of the curb. Park parallel to the street if there is no curb.
MARYLAND DRIVER'S HANDBOOK Parallel Parking When parking on a two-way roadway, you must park parallel to and within 12 inches of the curb or the edge of the roadway. When you take the test for your driver's license, you will have to show the examiner that you can park in a parallel parking space 6 feet wide and 25 feet long. This is a timed exercise.
set the parking brake, turn off the ignition switch and put the vehicle in low gear if your transmission is standard, and park, if it is automatic. The wheels should not be over twelve inches from the curb.
The person giving the test will have the discretion to pass or fail you on your parallel parking test.
18 inches
When parking uphill with a curb, turn your wheels away from the curb and set the parking brake. When parking uphill without a curb, turn your wheels towards the edge of the road or shoulder and use the parking brake. When parking downhill with a curb, turn your wheels towards the curb and use the parking brake. When parking downhill without a curb, turn your wheels towards the edge of the road or shoulder and use the parking brake.
A lot of people will go to a school or church parking lot to practice. Also you can find a quiet road with one or two cars parked at the curb, practice parallel parking behind just one vehicle, then when you're comfortable with how you park behind one vehicle, find two cars to park between.
That you can park for a limited time.
Yellow painted curb means "no parking"
If you refer to the parallel parking part of the "skills" test...it is 25' long and six feet deep. To pass, you have to park within 18" of the "curb." a former WV DMV troop.
12 inches from the curb
12 inches from the curb