Maximum Sizes and Weights for USPS services
Domestic Services:
First Class Package
Maximum Size: 22″ x 18″ x 15″ for boxes
18" x 18" for envelopes or poly mailers
Maximum Weight: 15.99 oz
Weight-Based Priority Mail
Maximum Size: 108” combined Length + Girth
Maximum Weight: 70 lbs (1120 ounces)
Priority Mail Cubic
Maximum Size: 18" in any dimension, total volume cannot exceed 0.5 cubic feet
Cubic Softpack Maximum Size: 36” combined Length + Width
Maximum Weight: 20 lbs (320 ounces)
Priority Mail Flat Rate
Maximum Weight: 70 lbs (1120 ounces)
Priority Mail Express
Maximum Size: 108” combined Length + Girth
Maximum Weight: 70 lbs (1120 ounces)
Parcel Select Ground
Maximum Size: 130” combined Length + Girth
Maximum Weight: 70 lbs (1120 ounces)
Priority Mail Regional Rate Box A
Maximum Weight: 15 lbs (240 ounces)
Priority Mail Regional Rate Box B
Maximum Weight: 20 lbs (320 ounces)
International Services:
First Class Package International:
Maximum Size: 24″ in any dimension, 36″ combined Length + Width + Height
Maximum Weight: 4 lbs (64 ounces)
Simple Export Rate:
Maximum Size: 24″ in any dimension, 36″ combined Length + Width + Height
Maximum Weight: 4 lbs (64 ounces)
Priority Mail International:
Maximum Size: 108” combined Length + Girth
Maximum Weight: 70 lbs (1120 ounces)
Priority Mail International Flat Rate:
Maximum Weight for Flat Rate Envelope and Small Flat Rate Box: 4 lbs (64 ounces)
Maximum Weight for Medium and Large Flat Rate Box: 20 lbs (320 ounces)
Priority Mail Express International:
Maximum Size: 79” combined Length + Girth
Maximum Weight: 70 lbs (1120 ounces)
Size Shipping Tips:
When shipping internationally, there may be differences in the maximum weight and dimensions based on what that country and USPS have agreed upon. You can check out those differences, as well as a full list of prohibited items per country here: https://pe.usps.com/text/Imm/ab_toc.htm
Look out for Dimensional Weight on your light, oversized packages: https://www.shippingschool.com/dimensional-weight/