Mailbox Height Requirements: How to Measure and Set Your Mailbox
What Are the Mailbox Height Requirements?
Mailbox height requirements for a curbside mailbox call for 41 to 45 inches from the road surface to the bottom of the mailbox or the point of mail entry, with the box set 6 to 8 inches back from the curb.
Wall, door and shared boxes follow other mailbox height rules:
| Mailbox | Height | Measured from |
|---|---|---|
| Curbside (post mount) | 41 to 45 inches; 6 to 8 inches back from the curb | Road surface to the bottom of the box or point of mail entry |
| Wall mount | No USPS height; near the main entrance | Not set |
| Door slot | Bottom at least 30 inches | Finished floor |
| Shared or multi-unit (4C, CBU) | Set by USPS-STD-4C or the unit’s pedestal | Finished floor or pad |
The rest of this guide shows how to measure it, pick a post that lands in range, and fix a box that doesn’t.
The USPS Rules Behind the 41 to 45 Inch Height
USPS sets these numbers in How to Install a Mailbox. Our USPS mailbox regulations guide covers the rest.
Height and Setback for Curbside Mailboxes
USPS asks for 41 to 45 inches from the road surface to the bottom of the mailbox or point of mail entry. The mailbox door should sit 6 to 8 inches back from the front face of the curb, or the road edge. No raised curb? Ask your local postmaster.
The Domestic Mail Manual sets no curbside height. It only asks for a box carriers can serve “without leaving their vehicles” (DMM 508, 3.2.6).
What USPS Says About Mailbox Posts
USPS doesn’t regulate posts beyond carrier safety and delivery. It points to Federal Highway Administration advice: a 4×4 wooden post or a 2-inch steel or aluminum pipe, buried no more than 24 inches.
Both should break away if a car hits them. Skip concrete posts, heavy metal pipe and concrete-filled milk cans. In snowy areas, USPS suggests a semi-arch or extended arm so plows can pass under the box.
Who Has the Final Say on Your Mailbox Height
Your local post office applies these mailbox height requirements to your route. Road and curb conditions vary, so USPS recommends checking with it before you put in or replace a mailbox or post. It can also notify you if your box doesn’t meet postal rules.
Placement must follow state laws and highway rules, and HOAs can limit post style and placement.
How to Measure Your Mailbox Height From the Road
How high off the ground should a mailbox be? For both mailbox height and distance from road, the ground that counts is the road, not your yard.
To measure mailbox height from road level:
- Stand where your carrier’s vehicle stops and find the road surface there.
- If your yard sits higher or lower than the road, run a level (or a straight board with a level) from the road edge to the post.
- Measure up from that line to the bottom of the mailbox, or to the slot on a slot-style box.
- Aim for about 43 inches, the middle of the range, which leaves 2 inches of room either way.
Your mailbox height from ground level in the yard can differ by inches, so go by the road.
How to Choose the Right Post Length
How long should a mailbox post be? Burial depth plus the mailbox post height above ground, adjusted for the box.
In-Ground Posts: Burial Depth and Exposed Height
Exposed height is the post above ground. With the box on top, it equals your target. Subtract any board under the box, or add the drop for a box hung from an arm. Total length is exposed height plus burial depth.
Worked example
Box on the post top, yard level with the road, 43-inch target. 43 inches exposed plus 24 buried means a 67-inch (5 ft 7 in) post. A yard 3 inches above the road drops the exposed part to 40 inches.
Standard mailbox post dimensions vary widely: our in-ground posts that list a length run 46 to 83 inches. Check yours against your total before you buy. For digging and concrete, see how to install a curbside mailbox.
Surface-Mount Posts on Concrete
A surface-mount post bolts to a slab or pad, so there’s no burial depth. The post’s full length plus the base plate sets the height.
Measure how far the pad sits above the road, then subtract that from your target. Confirm the surface mount mailbox post height before you buy, since you can’t add depth later. Every one we sell lists it, most often in the Dimensions table. You can compare mailbox posts by mount type.
Matching a New Mailbox to Your Post
Swapping the box can change the height on the same post. A box with a deeper base or a different mounting bracket can sit higher or lower than the old one. Measure the new box’s bottom-to-mount distance before you buy.
An existing post also rarely matches a new box’s mounting pattern. That’s why most replacements end up as a mailbox with post included, rather than two separate buys.
Setting the Height on Sloped Lots, Ditches and Raised Curbs
Putting a mailbox on a slope? Mailbox height requirements still start at the road. A yard higher than the road means less than 41 to 45 inches of exposed post. A lower yard means more.
By a drainage ditch or soft shoulder, ask the post office where they want the box before you dig. Set the post on firm ground so it can’t lean into the ditch.
With a raised curb, measure from the road surface, not the top of the curb. Keep the 6 to 8 inch setback from the curb face.
Rural routes use the same numbers. On new rural routes, the box must sit on the right-hand side of the road in the carrier’s direction of travel. See the post mount mailbox FAQ for more.
Fixing a Mailbox That’s Too High or Too Low
Most fixes are small once you know the real number. Work through them in order, easiest first:
- Measure again from the road surface. A yard that sits above or below the road gives a different reading.
- An inch or two low? Move the bracket or arm up, or add a mounting board.
- Too high? Move the bracket down or cut the post, then measure again before you refit the box.
- Post leaning or pushed up by frost heave? A lean drops the box too. Reset the post, or replace it if the base has rotted.
- Road repaved or regraded? Measure again, since a new road surface changes the number.
- Got a note from your carrier? Fix the height, then let your post office know.
Height Rules When Your Mailbox Isn’t at the Curb
Wall mounts, door slots and shared mailboxes follow different rules from curbside boxes.
Wall Mount Mailboxes
USPS sets no height for a wall mount mailbox, and it doesn’t need the PMG seal. You do need your local postmaster’s permission to replace a curbside box with one. Place it near the main entrance, where your carrier can see it.
Browse wall mount mailboxes, or read how to install a wall mount mailbox.
Door Slots
A door slot carries the one door-level height USPS sets. The bottom of the slot must sit at least 30 inches above the finished floor, with an opening at least 1-1/2 by 7 inches (DMM 508, 2.1.6). Browse mail slots and check each opening size.
Shared and Multi-Unit Mailboxes
Twin, triple and quad post sets follow the same 41 to 45 inch rule for each box. Indoor 4C units follow USPS-STD-4C and ADA reach ranges instead, and cluster box units are a separate USPS-licensed type. Our regulations guide covers both. For curbside sets, see our multi-family mailbox and post combos.
Why Our Mailbox and Post Combos Make the Right Height Easy
Our mailbox and post combos take the guesswork out of height. Each set arrives with its mounting pattern, post diameter and arm length matched at the factory, plus instructions in the box. You’ll know where the mailbox will sit before the post goes in.
Choose an in-ground post for a new install, or a surface-mount post for an existing pad. If your box is still in good shape, we sell posts separately too. You can compare designs from fourteen manufacturers under one roof, and orders over $30 ship free.
For personal help matching a box, post and height, call our team at 866-717-4943.
Mailbox and post combos
Know where your mailbox will sit before the post goes in
Mounting pattern, post diameter and arm length matched at the factory. Fourteen manufacturers, free shipping on orders over $30.
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Categorized in: Mailbox Installation & Upgrades, Residential Mailboxes