Postage for Large Envelopes & Flats

Looking to mail a large envelope? Here, you'll find up-to-date rates for mailing flats via the USPS as well as information on letter dimensions, requirements, and more.

USPS First Class Template Size Guide Ruler Measuring Tool Postal Slot Gauge Large Envelope Shipping Tool

Small Flat Rate Box - US Global Mail

The USPS Flatrate Envelope Rate

What Priority Mail Flat Rate® Envelopes Are Available?

USPS: Battle of the bulge - Cracking Down on Flat Rate Envelopes - ValueMailers

Postage for Square Envelopes

Summary of Domestic Changes

Division Facility Management

January 24, 2021 USPS Rate Increase: See How It Will Impact Your Budget