With USPS Flat Rate Envelopes, if it fits, it ships for one low rate. When sealing the envelope, the container flaps must be able to close within the normal folds. Learn more about USPS Flat Rate Envelope dimensions.
Most USPS Flat Rate Envelopes have a maximum contents weight of 70lbs.
View domestic and international package sizes and dimensions.
If you are shipping internationally, be sure to check the country restrictions to determine if lower weight limits apply.
For international shipments, USPS uses Country Price Groups to calculate shipping rates. Learn more about Country Price Groups.