How to check the mailbox and house numbers
USPS mailbox height requirements generally call for a curbside box 41 to 45 inches above the road surface, with its door 6 to 8 inches back from the curb. Your house number should be on the box and readable from the street. Check with your local post office before you move or replace anything.
Mailbox height requirements and house numbers to check
You're checking two separate things, because they serve different people. The mailbox has to work for a carrier who stays in the vehicle. The house numbers have to work for a driver or a fire crew looking for you at night.
Start by working out what kind of delivery you have. A curbside box is served from a vehicle. A wall-mounted box or door slot is served on foot. A cluster box unit is a shared bank of locked boxes, and USPS treats it as the approved option for new or replacement delivery in single-family and townhome developments. If you share a cluster box, the post office or your HOA handles most of what follows, and your only checks are that your key works and your compartment locks.
State and local rules can be stricter than USPS guidance. Your local post office is the first call, and USPS says to contact it before installing or replacing a box.
How to check mailbox height requirements at your curb
- Identify your delivery type
Curbside, wall-mounted, door slot or cluster box. The rest of the check depends on this.
- Test the box
Open and close the door, check for rust, and make sure the box is firmly attached to its post. Check the flag on full-service boxes.
- Measure height and setback
Use a tape from the road surface and from the curb edge. Write down both numbers.
- Shake the post
It should stand firm. Note if it's rotted, leaning or made of heavy rigid material.
- Read your numbers from the street
Stand at the road, in both directions, in daylight.
- Repeat after dark
If you can't read them from a car with the headlights on, add lighting or change the contrast.
- Call the post office before changes
Ask about height and placement, and who handles keys if you have a cluster box.
USPS mailbox rules for height, setback and posts
Measure a curbside box against the USPS guidance. Measure height from the road surface, not your lawn.
| Check | USPS guidance | If it's off |
|---|---|---|
| Height | 41 to 45 inches, to the bottom of the box or mail opening | Ask your post office, then reset the post |
| Setback | 6 to 8 inches back from the curb or road edge to the door | Ask your postmaster, especially with no raised curb |
| Approval | Marked Approved by the Postmaster General and U.S. Mail | Replace it, or get your postmaster to approve a custom box |
| Door | Pulls outward and downward, and closes fully | Repair or replace it |
| Post | 4x4 wood, or 2-inch steel or aluminum pipe, buried no more than 24 inches | Replace rigid posts |
| Number | House or apartment number shown on the box | Add it |
The post rules aren't cosmetic. Supports are meant to bend or break away if a car hits them, which is why USPS warns against heavy metal pipes and concrete posts. You own the post and its upkeep.
Door slots have their own rule. The opening should be at least 1.5 by 7 inches, with the bottom at least 30 inches above the floor.
For numbers on the house, fire codes set the standard and it varies. California's fire code, as quoted by one fire district, requires characters at least 4 inches high with a 1/2-inch stroke, in a color that contrasts with the background and is visible from the street. That's a sensible target anywhere unless your town says otherwise.
How to fix mailbox height or house numbers you can't read
If your box is the wrong height or setback, don't dig yet. Talk to the post office first, since road and curb conditions vary and they can tell you what will work on your street. Call 811 before you dig a new post hole, because shallow utility lines often run near the road edge.
If your numbers can't be seen, fix the cause. Trim the shrub, move the numbers or add a second set by the driveway. Where the house isn't visible from the road, a post or sign at the driveway entrance can do the job. Local fire departments often give advice on this, and your HOA may have its own style rules.
If the box is a cluster unit and the lock or door is broken, report it to your post office. Don't try to force it, since those units are shared with your neighbors.
What homeowners say about house number size and mailboxes
For a cluster box, the post office will change the lock for a fee; one owner paid about $40. Bring your deed or closing papers, photo ID and a utility bill to prove you own the house. (Reddit)
How high should a mailbox be? Common questions
How high should a mailbox be from the road?
USPS generally says 41 to 45 inches from the road surface to the bottom of the box or mail opening. Road conditions vary, so confirm with your local post office before you set a post.
Can I use a concrete or metal post for my mailbox?
USPS advises against rigid supports such as heavy metal pipes and concrete posts. A 4x4 wooden post or a 2-inch steel or aluminum pipe, buried no more than 24 inches, is the guidance because it can give way if a car hits it.
How big should house numbers be?
It depends on your local fire code. A common rule for homes is at least 4 inches high with a 1/2-inch stroke, in a color that contrasts with the background. Ask your fire department or building office what applies to you.
Sources: USPS, cvfpd.specialdistrict.org
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.