A mid-tower goes into a 24 × 20 × 20 inch carton. That is 9,600 cubic inches, which lands just under the 10,368 cubic inch mark where UPS and FedEx begin charging additional handling on volume by itself. It will be billed at 70 lb no matter what the scale says. Every carton below was quoted through the calculator on 2026-08-15, Berkeley Heights, NJ to Beverly Hills, CA.
A desktop machine is light for the space it occupies. Once the box passes about a cubic foot, the tape measure sets the price and the scale stops mattering.
Start with the machine, not the box. Cases cluster into four sizes, and knowing which one is on the desk gets you to a carton in one step. Measure over the rubber feet, over a top-mounted handle and over anything bolted to the back panel; a graphics card bracket and a thumbscrew both count, and both are what stops a lid from closing at 11pm.
| Chassis | Case, roughly | Carton at 3 in clearance | Cubic volume | Against the 10,368 line |
|---|---|---|---|---|
| Small form factor | 14 × 6 × 13 in | 20 × 12 × 19 in | 4,560 in³ | Well under |
| Micro-ATX tower | 17 × 8 × 15 in | 23 × 14 × 21 in | 6,762 in³ | Under |
| Mid-tower ATX | 18 × 9 × 18 in | 24 × 15 × 24 in | 8,640 in³ | Under |
| Full tower | 22 × 10 × 21 in | 28 × 16 × 27 in | 12,096 in³ | Over |
The mid-tower is the last chassis that clears the line with room to spare, and it clears it even if you skip the tape measure and buy a stock 24 × 20 × 20 in double-wall carton off the shelf: 9,600 cubic inches, still under. The useful rule of thumb is a 22 inch cube. At 10,648 cubic inches that is already over, so any carton whose three sides average much past 21 inches is into surcharge territory before a single component goes in.
A full tower cannot be padded properly and stay under. Plan for the additional handling charge, or strip the machine: pull the graphics card and the cooler into their own boxes and the case itself often drops a size band. The step-by-step version of that is on the PC packing guide.
Every row below is a quote returned on 2026-08-15 for the lane Berkeley Heights, NJ 07922 to Beverly Hills, CA 90210. The price shown is the cheapest service that came back, with SMKlog's charge already inside it.
| Machine | Carton | On the scale | Dimensional | Billed at | Cheapest quote |
|---|---|---|---|---|---|
| Mini PC | 12 × 10 × 6 in 720 in³ | 6 lb | 6 lb | 6 lb | $19.13 UPS Ground Saver |
| Small form factor desktop | 16 × 12 × 8 in 1,536 in³ | 14 lb | 12 lb | 14 lb | $23.77 USPS Ground Advantage |
| All-in-one desktop | 30 × 22 × 10 in 6,600 in³ | 28 lb | 48 lb | 48 lb | $69.03 UPS Ground |
| Mid-tower | 24 × 20 × 20 in 9,600 in³ | 35 lb | 70 lb | 70 lb | $94.53 UPS Ground |
| Mid-tower, roomier carton | 26 × 22 × 20 in 11,440 in³ | 35 lb | 83 lb | 83 lb | $117.05 UPS Ground |
The last two rows are the same machine at the same 35 lb, quoted the same day between the same pair of ZIPs. The only change is two inches of width and two inches of depth on the carton, and UPS Ground went from $94.53 to $117.05. FedEx Ground moved further on the same pair, $131.50 to $192.31. Thirteen pounds of billable weight appeared out of cardboard, and the roomier carton also crossed 10,368 cubic inches, which is where the additional handling charge starts.
A trailer fills up on volume long before it fills up on weight, and since January 2026 both networks price that directly instead of inferring it from length and girth. The practical consequence for a desktop machine is that padding bought in the wrong shape gets paid for twice.
Four numbers decide whether a boxed PC is an ordinary parcel, a surcharged one or something a carrier will not accept. All four were read from the carriers' own pages on 2026-08-15 and every one of them changed during 2026, so a figure remembered from last year is probably wrong.
| Threshold | Where it sits | What happens at it | A tower carton |
|---|---|---|---|
| Dimensional divisor | 139 at USPS, UPS and FedEx | Volume converts to pounds. USPS moved from 166 to 139 on 12 July 2026 and now rounds every measurement up to the next whole inch first. | 24 × 20 × 20 in bills at 70 lb |
| Additional handling | Over 10,368 in³ | A per-package charge on cubic volume alone, new for 2026. FedEx published its 2026 dimension charge at $29.50 in zone 2 rising to $40.75 in zone 7 and beyond. | 9,600 in³ is inside it |
| Large package and oversize | Over 17,280 in³ | A much larger per-package charge, and a 90 lb minimum billable weight applies however light the box is. | No desktop carton reaches this |
| Outer limits | 70 lb and 130 in at USPS; 150 lb, 108 in long and 165 in length plus girth at UPS and FedEx | USPS treats anything past its pair as nonmailable. UPS and FedEx bill an over maximum limits charge per package. | 104 in length plus girth, nowhere near |
Length plus girth on the 24 × 20 × 20 carton works out at 104 inches: the longest side, then twice the width plus twice the height. That is comfortably inside every ceiling on the list, which is the reassuring half of the story. The awkward half is that a desktop machine never gets near a weight limit and still costs like a heavy parcel, because volume is doing the work.
USPS is the one to watch on volume rather than size. Its published nonstandard fee adds $21.00 to anything over 2 cubic feet, which is 3,456 cubic inches, and a tower carton is nearly three times that. On the lane quoted above, no USPS service came back for any carton larger than the small form factor box, so the choice in practice was between the two ground networks.
Case dimensions first, three inches added to each face second, carton bought third. Doing it the other way round means padding a machine to fit a box somebody else sized, and that is how a 9,600 cubic inch job becomes an 11,440 cubic inch one.
A single-wall carton buckles at the corners under 30 lb and more cardboard around it does not fix that. One double-wall box with rigid cushioning beats two thin ones, and it keeps the outer dimensions honest.
Two parcels can beat one when the single carton would cross a threshold. A graphics card shipped separately in a 14 × 10 × 6 in box lets the case drop to a smaller carton, and it is also the component most likely to arrive broken.
The calculator takes a plain description and a pair of ZIP codes and prices USPS, UPS and FedEx together, so the box you are holding can be compared against the box you were about to buy before either one is taped shut. For a monitor traveling in the same shipment, the carton rules are different enough to be worth reading on their own: see monitor shipping boxes.
Carriers revise these without notice and each publishes its own tariff. Treat everything above as what those pages said on the date shown, and check the carrier actually moving your box.
A mid-tower ATX case measures roughly 18 × 9 × 18 in, so with three inches of clearance on every face the carton lands near 24 × 15 × 24 in. Buy a stock 24 × 20 × 20 in double-wall carton instead of cutting one down and you are at 9,600 cubic inches, still under the 10,368 cubic inch line. A full tower does not fit that budget.
A small form factor case runs about 14 × 6 × 13 in, a micro-ATX tower about 17 × 8 × 15 in, a mid-tower ATX about 18 × 9 × 18 in and a full tower about 22 × 10 × 21 in. Measure over the rubber feet, the top handle and anything screwed to the back panel, because the carton has to clear all of it.
Dimensional weight, almost every time. USPS, UPS and FedEx all divide length × width × height by 139 and round up. A 24 × 20 × 20 in carton works out at 70 lb of billable weight whether the machine inside weighs 25 lb or 45 lb.
It is the first one. Since January 2026 both UPS and FedEx assess additional handling on cubic volume alone above 10,368 cubic inches, with no reference to weight. The second line is 17,280 cubic inches, where the charge becomes a large package or oversize charge with a 90 lb minimum billable weight attached.
On size and weight, yes: a tower carton is far inside the 70 lb and 130 inch length-plus-girth ceiling. USPS publishes a $21.00 nonstandard fee on anything over 2 cubic feet, though, and on the lane quoted here no USPS service came back at all for cartons above small form factor size.