If you want to send letter-sized papers without folding them, you can use a large envelope (called a "flat"); the postage for flats starts at $1.50. If your large envelope is nonrectangular, rigid (can't bend), or lumpy (not uniformly thick), you'll have to pay the package price.

The maximum size for a flat provides plenty of room to put lots of material in the envelope. But keep in mind that weight usually affects price – the higher the weight the higher the postage, especially for First-Class Mail.

Large Package Any dimension over 12 inches (30.48 cm)

First-Class Mail is a fast, low-cost way to send envelopes and postcards. See First-Class Mail and Forever stamp prices for a letter and postcard.

Flat Rate shipping lets you send your items for a low Flat Rate price. See the Flat Rate Quick Reference section for additional details, including international weight restrictions and options. Calculate Postage for the shape, weight, and destination of your mail at pe.usps.com.

Priority Mail Express and Priority Mail envelopes are available at your Post Office or visit www.usps.com/store. You must use the USPS-produced address label for Priority Mail Express.

contains items that cause more than 1/4 inch variation in thickness

Learn how to ship a package with USPS, from choosing the right mail service, packing your box, writing the address, calculating postage, and scheduling a pickup.

USPS postage rates offer low-cost mailing and shipping prices for domestic & international customers. See Forever postage stamp prices and other postage rates.

With our free Flat Rate Envelopes, you don’t need to weigh shipments 70 lbs and under. Purchase Priority Mail Express postage and shipping labels at a Post Office ™ location or online.