Post office boxes (also called postal boxes or PO boxes) come in several different sizes. To choose the size that will suit your needs, consider how much mail you think you’ll receive and whether it will include packages. 

Postal box specifications Size Description Dimensions
Small Ideal for letter envelopes 90 mm x 130 mm x 360 mm
Medium Accommodates letter, legal and large brown envelopes 140 mm x 130 mm x 350 mm
Large ... 290 mm x 130 mm x 360 mm
X-Large Accepts virtually all size letters, envelopes and various sized parcels 290 mm x 270 mm x 360 mm
XX-Large ... 600 mm x 280 mm x 360 mm
Container/bag service Ideal for customers who receive large volumes of mail ...

All sizes may not be available at every post office location. Please check with the post office to make sure the type of box you need is available.  Find a post office.