How long is the validity of American patents?

American invention patents are valid for 20 years from the date of filing;

American design patents are calculated from the date of authorization:

For an application for a patent for American appearance filed before May 20 13 15, the protection period after authorization is 14 years from the date of authorization;

For an application for a patent for American appearance filed after May 20 15 13, the protection period after authorization is from the date of authorization 15.