Packed box
20 × 18 × 10 in
20 lb
Electronics
The coin cell in a desktop removes one USPS rule and hands you another
Yes, a computer ships. The part nobody expects is that the smallest battery in the machine is the one that decides which carrier will take it. The coin cell on a desktop motherboard is small enough that USPS drops the lithium marking entirely — and small enough that the same instruction caps the whole package at 5.5 pounds. A boxed tower is nowhere near that, which is a big part of why our own live capture came back with UPS and FedEx rates and nothing from USPS at all.
USPS rule, quotedRead 2026-08-22Live checkout rates
Coin cell, not a rechargeable pack
A CMOS battery is a button cell: no lithium mark, but a 5.5 lb package cap comes with it.
What the coin cell does, and then undoes
USPS Publication 52 defines the component by name. A Button Cell Battery is “a small, single-cell round battery with a diameter greater than its height… often installed in electronic devices as auxiliary power sources,” and a mailable one must hold “no more than 0.3 grams of lithium for lithium metal types.” A CR2032-style CMOS cell, the battery every desktop motherboard uses to hold the clock and BIOS settings through a power-off, is that part exactly.
What it removes. Section 349.221 lists the marking rule and then excepts this case outright: mailpieces containing “button-cell batteries installed in equipment (including circuit boards)… are excepted” from the DOT lithium battery mark. So no UN number goes on the outside of a desktop's box, and none of the Restricted Electronic Device wording a used phone or laptop carries applies either. That much of the intuition is right.
What it adds. The exception is only from the mark, not from the instruction. Section 349.232, covering cells installed in the equipment they operate, sets the weight tiers: “For cells and batteries containing up to 0.3 grams of lithium, no mailpiece may exceed 2.5 kilograms (5.5 pounds). There is no maximum number of cells or batteries per mailpiece.” The tier above it, for cells over 0.3 grams, allows 5 kilograms (11 pounds) and caps the count at eight cells or two batteries. Read as printed, a package holding a motherboard with its coin cell in place sits in the first tier, and the tower in our capture below weighed 20 lb boxed — nearly four times that ceiling.
That is the whole shape of it: the smallest battery in the machine is what puts a full desktop outside USPS's lithium-battery lane, while the far larger pack in a laptop keeps that machine comfortably inside it. This is a USPS rule and only a USPS rule; it says nothing about what UPS or FedEx will carry, and both of them priced the tower below without incident.
A live quote: desktop computer tower in original box
Captured 2026-08-22 through the SMKlog calculator: “Desktop computer tower in original box”, Berkeley Heights, NJ 07922 to Phoenix, AZ 85001.
Route
Berkeley Heights, NJ
to Phoenix, AZ
Declared as
New in original box
No lithium battery declared
| Carrier | Service | Price | Transit |
|---|---|---|---|
| UPS | Ground | $45.48 | 4-5 business days |
| FedEx | Ground Economy | $52.18 | 8-9 business days |
| UPS | Ground Saver | $63.42 | 6 business days |
| FedEx | Ground | $69.83 | 5-6 business days |
| UPS | 3 Day Select | $72.53 | 3-4 business days |
No USPS service priced this box on this route. UPS and FedEx covered the entire list, and nothing in the shipment was flagged as hazardous or held for review at any point — the box simply came back with two carriers on it instead of three. Worth noting what does not explain the gap: at 20 lb and 76 inches of length plus girth, this box sits far inside USPS Ground Advantage's published 70 lb and 130 inch ceilings. The 5.5 pound tier in section 349.232 is the rule that fits the outcome, but a rate engine does not tell you which rule it applied, so treat that as the reading that matches rather than a proven cause.
UPS Ground was cheapest here at $45.48, roughly four times the one-pound phone examples elsewhere on this site. That part really is just the volume and weight of a tower.
Packing a tower for its second trip
Secure the inside first
Add-in cards, loose drive bays and anything on a ribbon cable can shift and pry itself loose under vibration. Pull what you can, tape down the side panel, and pack the internal gaps before the case ever goes into an outer box.
Float it, don't hug it
The retail box a tower shipped in from the factory is usually snug, not cushioned for a second trip through a sort facility. Give the case at least 2 inches of foam or crumpled paper on every side inside a larger outer box.
Weigh and measure the finished box
Case weights vary far more than people expect, and the sealed carton is what gets billed — on actual or dimensional weight, whichever is higher. Put the real numbers into the quote rather than a spec-sheet figure, especially if you are anywhere near a carrier's surcharge line.
A laptop, an all-in-one, or anything else with a built-in rechargeable battery is a different shipment: see shipping a laptop for the UN3481 rule that applies there instead. For where USPS's plain size and weight ceiling bites on smaller machines — a mini desktop does get quoted — see computers through USPS.
Where these rules come from
- USPS, Publication 52, section 349 (Class 9 Hazardous Materials) — the button cell definition in 349.2, the marking exception in 349.221, and the installed-in-equipment weight tiers in 349.232 (2.5 kg / 5.5 lb at or below 0.3 gram of lithium; 5 kg / 11 lb above it). Read 2026-08-22.
- USPS, Publication 52, Packaging Instruction 9D — the same limits restated as a mailability exhibit, including the 5.5 lb mailpiece column for very small consumer-type batteries contained in equipment. Read 2026-08-22.
- USPS, Ground Advantage — the 70 lb and 130 inch service limits our example box sits inside. Read 2026-08-22.
- Prices: our own capture against production for the desktop tower parcel above, Berkeley Heights, NJ 07922 to Phoenix, AZ 85001, run 2026-08-22. Not list prices and not estimates.
USPS revises Publication 52 without notice, and carrier size and weight limits change independently of the battery rules described here. Publication 52 also states the tiers above without spelling out how a retail clerk applies them to a 20 lb machine holding a single coin cell, so treat this page as a reading of the printed text on the date shown, not a ruling. Confirm at the counter before mailing anything unusual.
Common questions
Can you ship a computer?
Yes. To UPS and FedEx a desktop tower is an ordinary heavy parcel, and both priced one in our capture on 2026-08-22. USPS is the awkward carrier here, and not for the reason most people expect: the coin cell soldered onto the motherboard pulls the package into USPS Publication 52's lithium-battery instruction, and that instruction sets a package weight cap a tower cannot meet.
Does a desktop need the lithium battery marking a laptop needs?
No. Publication 52 section 349.221 excepts mailpieces containing button-cell batteries installed in equipment, including circuit boards, from the DOT lithium battery mark. A CMOS motherboard cell is exactly that, so no UN number goes on the outside of the box.
Then why is USPS still complicated for a desktop?
Because the same instruction that removes the mark sets a weight tier. Section 349.232 states that for cells and batteries containing up to 0.3 grams of lithium installed in equipment, no mailpiece may exceed 2.5 kilograms (5.5 pounds), with no limit on the number of cells. The tier above it, for cells over 0.3 grams, stops at 5 kilograms (11 pounds). A boxed tower clears neither number.
Did USPS actually quote a desktop tower?
Not in our capture. A 20 x 18 x 10 in, 20 lb tower run from Berkeley Heights, NJ 07922 to Phoenix, AZ 85001 on 2026-08-22 returned five rates, every one of them UPS or FedEx. That box sits well inside USPS Ground Advantage's 70 lb and 130 inch limits, so plain size does not explain the absence. We cannot see which rule a rate engine applied, only that the printed rule and the empty result point the same direction.
How should a desktop tower be packed?
Pull any add-in cards that rattle loose, tape down the side panel, and fill the case's internal air gaps with foam or paper so the motherboard cannot flex against its standoffs. Then float the whole tower inside an outer box with at least 2 inches of cushioning on every side; the original retail box rarely has enough padding on its own for a second trip.
Does a laptop or all-in-one follow the same rule?
No. A laptop or an all-in-one carries a real rechargeable pack, far above the button-cell line, so it ships under the UN3481 rule with the mark that requires. It is also light enough that USPS's own weight tiers are reachable, which a tower is not.