USPS requires a curbside mailbox to be mounted so the bottom of the box is 41 to 45 inches above the road surface, with the front of the box set 6 to 8 inches back from the face of the curb (or the edge of the road where there is no curb). The box must carry the house number, sit on the carrier's side of the street, and be mounted on a post that will give way if a vehicle hits it. Manufactured boxes carrying the Postmaster General's seal meet USPS construction standards; anything custom should be shown to your local postmaster before installation.
Key facts
- Height: 41"–45" from road surface to the bottom of the mailbox.
- Setback: 6"–8" from the curb face to the mailbox door.
- Post: USPS cites the Federal Highway Administration's recommendation of a 4"×4" wood post or a 2"-diameter steel or aluminum pipe, buried no more than 24" deep. Avoid heavy pipe, concrete-filled posts, or masonry.
- Numbers: put your house number on the box; if the box is on a different street, use the full street address.
- Approval: a box with the Postmaster General's seal is pre-approved; custom boxes need local postmaster sign-off.
- Wall-mounted switch: replacing a curbside box with a wall-mounted one requires postmaster permission.
Why does USPS regulate where my mailbox goes?
Because carriers deliver from the vehicle without getting out. The 41"–45" window puts the box at the window height of the delivery vehicle; the 6"–8" setback lets the carrier reach the door without leaving the lane or hitting the box with the mirror. Getting either wrong means slower delivery for the whole route, which is why carriers do notice and do leave notes.
What are the exact height and distance rules?
| Measurement | Requirement | Measured from |
|---|---|---|
| Height | 41"–45" | Road surface to the bottom of the mailbox (the mail entry point) |
| Setback | 6"–8" | Curb face (or road edge) to the front of the mailbox door |
| Post depth | No more than 24" | Grade to bottom of post |
If your street has no curb, measure from the edge of the pavement or the shoulder line. Where snow is plowed, the box still has to be reachable; some rural districts allow a slightly greater setback or a swing-away post — ask the local post office before assuming.
What kind of post does USPS allow?
USPS defers to the Federal Highway Administration on this point, and the reason is safety rather than delivery: a mailbox post is a roadside object that cars hit. The recommended supports are a 4"×4" wooden post or a 2"-diameter standard steel or aluminum pipe, buried no more than 24" deep, so the post yields on impact. USPS specifically warns against "unyielding and potentially dangerous supports, like heavy metal pipes, concrete posts, and farm equipment."
A powder-coated steel tube post in the 1¼"–2" range with a plate base is consistent with this guidance; a brick pier or a 6"-diameter concrete-filled column is not, and in some states it is a liability for the homeowner.
What has to be on the mailbox?
Your house number, in figures at least 1" high, on the door or the side facing the carrier's approach. If the box is on a street other than the one in your address, put the full street address on it. Names are optional. Numbers should contrast with the box color; black on white, white on black, or aluminum on a saturated color all read well.
Does my mailbox have to be "USPS approved"?
There are two paths. Manufactured curbside boxes can go through the USPS approval program under USPS-STD-7 and carry the Postmaster General's seal; these are automatically acceptable. Boxes without the seal — custom-built, imported, or simply never submitted — are not automatically prohibited; USPS says to show your local postmaster the box or the plans for approval. In practice, carriers accept a front-opening box that holds standard mail, has a functional door and flag, and is mounted correctly. If you're unsure, take a photo to the post office before you dig the hole.
The 2015 standard (USPS-STD-7C) recognizes four categories: Traditional (the classic dome-top form), Contemporary (any other shape meeting the same capacity), Locked Mail Slot (a locking box with a mail opening) and Locked Large Capacity. It's worth knowing that "Contemporary" has been USPS's own term for non-traditional, mid-century-style boxes since at least 1970.
What are the rules for locking mailboxes?
Under USPS-STD-7C, a locking curbside box submitted for approval must have a mail slot at least 1¾" high by 10" wide so the carrier can insert magazines and flats without a key. Carriers do not carry keys to private mailboxes. If a locking box's slot is too small, the carrier will leave larger items elsewhere or return them. Adjustable-slot designs let you set the opening; make sure the setting you use still accepts your typical mail.
What about wall-mounted mailboxes and door slots?
Wall-mounted boxes go near the main entrance where the carrier can see them. If you currently have curbside delivery, you need the postmaster's permission to change to a wall box. Door slots have their own rules: the opening must be at least 1½" × 7", the bottom of the slot at least 30" above the floor, and a horizontal slot must have a flap hinged at the top.
Which side of the street does the box go on?
The carrier's side, at the location the post office designates; USPS guidance for new routes is the right-hand side of the road in the direction of travel. On a new route or a new address, the post office assigns the location; on an existing address, replace the box where the old one was. If you want to move it, ask first.
Common mistakes
- Measuring height to the top of the box, or to the top of the post, instead of to the bottom of the box.
- Setting the box flush with the curb because it "looks neater." Six to eight inches is the rule.
- Pouring a concrete footing around a heavy steel post. It's a hazard and can be ruled out by the highway department in some jurisdictions.
- Numbers too small to read from a moving vehicle.
- Locking box with a slot that won't take a magazine.
Where Modbox fits
Modbox's angled and vertical curbside posts are 1¼" square steel tube with a plate base, in line with the yielding-support guidance, with installation instructions on each product page; measure to confirm the finished box lands in the 41"–45" window. The Aerobox locking curbside box has an adjustable latch with four openings (½", 1", 1½", 2"); set it to the largest opening that meets your security needs so flats still fit. Address plates and numbers are available in the same colors as the boxes.
Frequently asked questions
How high should a mailbox be? 41 to 45 inches from the road surface to the bottom of the box.
How far from the curb should a mailbox be? 6 to 8 inches from the curb face to the front of the mailbox.
Can I put a mailbox in a brick pillar? USPS points to FHWA guidance against rigid supports. Some local post offices tolerate existing masonry; check locally before building one, and expect liability if a vehicle hits it.
Do I need to tell the post office when I replace my mailbox? Not if it's the same type in the same location. Tell them if you change location, change type, or switch to a locking box.
Is there a rule about mailbox color? No. USPS-STD-7C only specifies that the flag should contrast with the box (fluorescent orange is preferred). The box itself can be any color.
Sources
- USPS, "How to Install a Mailbox" — https://www.usps.com/manage/mailboxes.htm
- USPS-STD-7C, Standard Mailboxes, Curbside (September 14, 2015) — https://about.usps.com/publications/engineering-standards-specifications/spusps-std-7c.pdf
- Federal Register, "Standards Governing the Design of Curbside Mailboxes" (August 14, 2015) — https://www.federalregister.gov/documents/2015/08/14/2015-20033/standards-governing-the-design-of-curbside-mailboxes