Shipping Box Sizes Chart: Standard Box Dimensions (in & cm)

Standard shipping box sizes chart

These are the stock corrugated box sizes carried by most packaging suppliers in the US. All figures are inside dimensions. The last column is the billable dimensional weight at the 139 divisor that USPS, UPS and FedEx all use in 2026 (each inch rounded up first; result rounded up to the next pound).

Common shipping box sizes with volume and dimensional weight
Inside size (in)	Size (cm)	Volume	Dim weight	Typical contents
6 × 6 × 6	15.2 × 15.2 × 15.2	216 cu in (3.5 L)	2 lb	Mugs, small parts, cosmetics
8 × 6 × 4	20.3 × 15.2 × 10.2	192 cu in (3.1 L)	2 lb	Phone accessories, small books
10 × 8 × 6	25.4 × 20.3 × 15.2	480 cu in (7.9 L)	4 lb	Small electronics, a candle set
12 × 9 × 6	30.5 × 22.9 × 15.2	648 cu in (10.6 L)	5 lb	Folded clothing, a pair of shoes in its box
12 × 12 × 6	30.5 × 30.5 × 15.2	864 cu in (14.2 L)	7 lb	Records, flat kitchenware
12 × 12 × 12	30.5 × 30.5 × 30.5	1 cu ft (28.3 L)	13 lb	All-purpose cube
14 × 10 × 8	35.6 × 25.4 × 20.3	0.65 cu ft (18.4 L)	9 lb	Boots, small appliances
16 × 12 × 8	40.6 × 30.5 × 20.3	0.89 cu ft (25.2 L)	12 lb	Multi-item orders
16 × 12 × 12	40.6 × 30.5 × 30.5	1.33 cu ft (37.8 L)	17 lb	Books, small moving box
14 × 14 × 14	35.6 × 35.6 × 35.6	1.59 cu ft (45 L)	20 lb	Countertop appliances
18 × 18 × 18	45.7 × 45.7 × 45.7	3.38 cu ft (95.6 L)	42 lb	Bedding, lamps, bulky light items
20 × 20 × 20	50.8 × 50.8 × 50.8	4.63 cu ft (131 L)	58 lb	Pillows, toys, cushions
24 × 18 × 18	61 × 45.7 × 45.7	4.5 cu ft (127 L)	56 lb	Small furniture parts
24 × 24 × 24	61 × 61 × 61	8 cu ft (226.5 L)	100 lb	Large, light items

The dimensional weight column shows why oversized boxes are expensive. An 18 × 18 × 18 box holding 8 lb of bedding is billed as 42 lb. Dropping to a 16 × 12 × 12 box, if the contents compress into it, cuts the billable weight to 17 lb. The full method and divisors are on the dimensional weight page.

How box dimensions are measured

A box listed as 12 × 9 × 6 means length × width × depth, measured on the inside:

Length is the longer side of the opening (12 in).
Width is the shorter side of the opening (9 in).
Depth is the height from the opening to the floor of the box (6 in).

So a 12 × 9 × 6 box opens on its 12 × 9 face, while a 12 × 6 × 9 box has the same volume but opens on a narrower face and is deeper. The outside is larger by roughly twice the board thickness on each axis: about ¼-⅜ in for single-wall C-flute board, about ½ in for double-wall. Carriers measure the outside, so a 12 × 12 × 12 box is billed as 13 × 13 × 13 after rounding up, which is 2,197 cu in and 16 lb of dimensional weight rather than 13 lb.

Rounding catches people out

Since August 2025 (UPS and FedEx) and July 12, 2026 (USPS), every fractional inch is rounded up before the dimensional weight is calculated. A box measuring 12¼ in on each side outside is billed as 13 × 13 × 13. Measure the outside and choose boxes whose outer size lands just under a whole inch.

Moving box sizes

Moving boxes are sold by name, not by dimensions, and the names are not standardized. These are the typical sizes from truck-rental and moving-supply retailers; U-Haul's medium, large and extra-large boxes match them.

Typical moving box sizes
Box	Size (in)	Size (cm)	Volume	Pack it with
Small	16 × 12 × 12	41 × 30 × 30	1.3 cu ft	Books, canned food, tools (heavy items)
Medium	18 × 18 × 16	46 × 46 × 41	3.0 cu ft	Kitchenware, toys, small appliances
Large	18 × 18 × 24	46 × 46 × 61	4.5 cu ft	Linens, lampshades, pillows
Extra-large	24 × 18 × 24	61 × 46 × 61	6.0 cu ft	Comforters, cushions, bulky light items

Note that many "1.5 cu ft" small boxes are actually 16 × 12 × 12 in, which is 1.33 cu ft; the label is rounded. The rule for moving boxes is the opposite of shipping: the heavier the contents, the smaller the box. A small box full of books weighs 30-40 lb, about the limit for comfortable carrying. For how many boxes fit in a unit or truck, see the storage unit size guide.

USPS flat rate box sizes

Priority Mail Flat Rate boxes ship anything up to 70 lb anywhere in the US for one price per box, so the useful question is what fits inside.

USPS Priority Mail Flat Rate box dimensions (2026)
Box	Inside (in)	Inside (cm)	Outside (in)
Small	8⅝ × 5⅜ × 1⅝	21.9 × 13.7 × 4.1	8 11/16 × 5 7/16 × 1¾
Medium (top-loading)	11 × 8½ × 5½	27.9 × 21.6 × 14	11¼ × 8¾ × 6
Medium (side-loading)	13⅝ × 11⅞ × 3⅜	34.6 × 30.2 × 8.6	14⅛ × 12 × 3½
Large	12 × 11¾ × 5½	30.5 × 29.8 × 14	12¼ × 12 × 6

Flat rate pays off for dense items. A 20 lb box of tools in the Large flat rate box costs one fixed price; the same weight in a regular box would be billed on weight and distance. For light, bulky items, a regular Priority Mail or Ground Advantage box is usually cheaper.

Carrier size and weight limits

Length + girth is the longest side plus twice the sum of the other two. For a 24 × 18 × 18 box: 24 + 2 × (18 + 18) = 96 in.

Maximum package size by carrier (US domestic, 2026)
Carrier	Max weight	Max length	Max length + girth	Surcharges start at
USPS Priority Mail	70 lb	within girth limit	108 in	Over 22 in long; over 2 cu ft
USPS Ground Advantage	70 lb	within girth limit	130 in	Over 108 in length + girth (oversized price)
UPS	150 lb	108 in	165 in	Longest side over 48 in, second side over 30 in, or over 50 lb
FedEx Ground	150 lb	108 in	165 in	Same additional-handling triggers as UPS

USPS bills dimensional weight only on boxes over 1 cubic foot (1,728 cu in), so a 12 × 9 × 6 box ships at its actual weight with USPS, while UPS and FedEx bill it at its dimensional weight (5 lb) whenever the contents weigh less than that. Check each carrier's current service guide before a large shipment, because surcharge thresholds change most years.

How strong a box you need

The round stamp on the bottom flap (the box maker's certificate) states the board grade. Two ratings are in use: edge crush test (ECT), which predicts stacking strength, and the older bursting test in pounds. Each grade has a maximum contents weight and a maximum size in "united inches" (length + width + depth).

Single-wall corrugated box ratings
ECT rating	Burst equivalent	Max contents	Max L + W + D
23 ECT	125 lb	20 lb	50 in
26 ECT	150 lb	35 lb	60 in
29 ECT	175 lb	50 lb	75 in
32 ECT	200 lb	65 lb	75 in
40 ECT	250 lb	80 lb	80 in
44 ECT	275 lb	95 lb	85 in

Standard stock boxes are 32 ECT. An 18 × 18 × 18 box is 54 united inches, well within the 75 in limit; a 24 × 24 × 24 box is 72 in, close to it, which is why heavy loads in large boxes call for double-wall board (48 ECT and up).

Choosing the right box for an item

Measure the item at its widest points, including handles and knobs.
Add cushioning on every side. UPS and FedEx packaging guidelines call for at least 2 in of cushioning around fragile items, which adds 4 in to each dimension. Durable items like clothing need about 1 in, or none in a padded mailer.
Pick the smallest stock box that clears all three numbers. A 9 × 6 × 3 in glass item needs 13 × 10 × 7 in; a 14 × 10 × 8 in box fits.
Compare the dimensional weight with the real weight. If the dim weight is much higher, look for a box one size down or cut the box down to the height of the contents.
For very fragile items, double-box: wrap the item in a box with 2 in of cushioning, then place that box in a larger one with another 2-3 in on all sides.

For packing shoes, see shoe box sizes; for clothing in luggage, packing cube sizes. Freight that goes beyond parcel limits moves on pallets or in shipping containers.

Frequently asked questions

What are the standard shipping box sizes?

The sizes stocked by nearly every packaging supplier are 6 × 6 × 6, 8 × 6 × 4, 10 × 8 × 6, 12 × 9 × 6, 12 × 12 × 6, 12 × 12 × 12, 14 × 10 × 8, 16 × 12 × 8, 16 × 12 × 12, 18 × 18 × 18, 20 × 20 × 20 and 24 × 24 × 24 inches (inside length × width × depth).

What does L × W × H mean on a box?

Length is the longer side of the opening, width the shorter side of the opening, and depth (height) the distance from the opening to the bottom. Suppliers quote inside dimensions. A 12 × 9 × 6 box therefore has a 12 × 9 in opening and is 6 in deep.

What size is a large shipping box?

Suppliers usually call boxes from about 18 × 18 × 18 in (3.4 cu ft) to 24 × 24 × 24 in (8 cu ft) large. A large moving box is typically 18 × 18 × 24 in (4.5 cu ft). Beyond 24 in on a side, UPS and FedEx additional-handling fees start to apply once the longest side passes 48 in or the second-longest passes 30 in.

What box sizes does the US Postal Service give for free?

Priority Mail Flat Rate boxes: Small 8⅝ × 5⅜ × 1⅝ in, Medium top-loading 11 × 8½ × 5½ in, Medium side-loading 13⅝ × 11⅞ × 3⅜ in, and Large 12 × 11¾ × 5½ in (inside). Any weight up to 70 lb ships for one price per box.

How much weight can a cardboard box hold?

It depends on its rating, printed in the round box maker's certificate on the bottom flap. A standard 32 ECT (200 lb burst) single-wall box is rated for up to 65 lb of contents and a maximum of 75 inches of length + width + depth. Double-wall boxes go to 80-180 lb.