KANSAS CITY, Mo. -- Monday is expected to be the busiest shipping day of the year, FedEx and U.S. postal officials said.

But some online retailers are offering savings if you wait a few days.

Thursday, Dec. 18, is being called Free Shipping Day by some online retailers. On that day, many stores, including Macy's, Crate and Barrel, Target and Nordstrom, will ship your purchases for no cost, saving shoppers from dealing with parking and crowds.

Participating retailers guarantee that gifts bought by Dec. 18 will arrive in time for Christmas.

For more information on Free Shipping Day, visit freeshippingday.com.

Postal officials at the Kansas City processing and distribution center said they expect to sort more than 2 million pieces of mail on Monday night, about three times the average mail volume.

Many people in line at the Johnson County post office near Metcalf Avenue and Johnson Drive said the line wasn't as bad as they anticipated on Monday morning.

"I'm sending these to my grandkids in Chicago and the South Dakota grandkids, so it was important that I come and brave it so it gets there on time," said Louis Kellogg.

Postal employees said regular mail needs to be sent by Tuesday to ensure arrival before Christmas. Priority mail can be sent by Friday.

Postal officials said postage can be printed from your home computer at a discount.