Cubic Feet of a Box Chart: Volume of 60 Standard Box Sizes

Updated August 22, 202660 stocked sizesInside and outside volume

Cubic feet equals length x width x height in inches divided by 1,728. This chart does the arithmetic for 60 stocked box sizes in cubic inches, cubic feet and liters, marks the two USPS volume lines that change a parcel's price, and runs the other way from a cubic foot target to the sizes that match it.

Cubic feet of a box: the formula

Multiply length by width by height in inches to get cubic inches, then divide by 1,728 (12 x 12 x 12) to get cubic feet. A 12 x 12 x 12 box is exactly 1 cubic foot inside. An 18 x 18 x 18 box is 5,832 cubic inches, or 3.375 cubic feet. For liters, multiply cubic inches by 0.01639. Use inside dimensions to find out what fits and outside dimensions to find out what the carrier or the truck sees; single wall corrugated adds about 1/4 inch to each axis, which moves a 12 x 12 x 12 box from 1.00 to 1.06 cubic feet.

Worked example: 16 x 12 x 8: 16 x 12 x 8 = 1,536 cubic inches. 1,536 / 1,728 = 0.89 cubic feet. 1,536 x 0.01639 = 25.2 liters. Outside: 16.25 x 12.25 x 8.25 = 1,642 cubic inches, 0.95 cubic feet, still under the USPS 1 cubic foot line.

Volume chart for 60 stocked box sizes

Sorted from smallest to largest footprint. The USPS column marks the two volume lines that change a parcel's price: above 1 cubic foot (1,728 cubic inches, measured on outside dimensions) USPS applies dimensional weight with divisor 139, and above 2 cubic feet (3,456 cubic inches) it adds a nonstandard volume fee. Both come from the Domestic Mail Manual, section 133, and Notice 123 effective July 12, 2026. UPS and FedEx apply dimensional weight at every size, so for them the cubic inches column is the number that matters.

Inside volume from the listed inside dimensions; outside volume adds 1/4 inch per axis for single wall board.
Box size (in, inside) Cubic inches Cubic feet (inside) Cubic feet (outside) Liters USPS volume line
4 x 4 x 4 64 0.04 0.04 1.0 Under 1 cu ft
5 x 5 x 5 125 0.07 0.08 2.0 Under 1 cu ft
6 x 4 x 4 96 0.06 0.07 1.6 Under 1 cu ft
6 x 6 x 4 144 0.08 0.10 2.4 Under 1 cu ft
6 x 6 x 6 216 0.12 0.14 3.5 Under 1 cu ft
7 x 7 x 7 343 0.20 0.22 5.6 Under 1 cu ft
8 x 6 x 4 192 0.11 0.13 3.1 Under 1 cu ft
8 x 8 x 4 256 0.15 0.17 4.2 Under 1 cu ft
8 x 8 x 6 384 0.22 0.25 6.3 Under 1 cu ft
8 x 8 x 8 512 0.30 0.32 8.4 Under 1 cu ft
9 x 6 x 4 216 0.12 0.14 3.5 Under 1 cu ft
9 x 9 x 9 729 0.42 0.46 11.9 Under 1 cu ft
10 x 6 x 4 240 0.14 0.16 3.9 Under 1 cu ft
10 x 8 x 6 480 0.28 0.31 7.9 Under 1 cu ft
10 x 10 x 6 600 0.35 0.38 9.8 Under 1 cu ft
10 x 10 x 8 800 0.46 0.50 13.1 Under 1 cu ft
10 x 10 x 10 1,000 0.58 0.62 16.4 Under 1 cu ft
11 x 8 x 6 528 0.31 0.34 8.7 Under 1 cu ft
12 x 6 x 6 432 0.25 0.28 7.1 Under 1 cu ft
12 x 8 x 6 576 0.33 0.37 9.4 Under 1 cu ft
12 x 9 x 6 648 0.38 0.41 10.6 Under 1 cu ft
12 x 9 x 9 972 0.56 0.61 15.9 Under 1 cu ft
12 x 10 x 6 720 0.42 0.45 11.8 Under 1 cu ft
12 x 10 x 8 960 0.56 0.60 15.7 Under 1 cu ft
12 x 12 x 4 576 0.33 0.37 9.4 Under 1 cu ft
12 x 12 x 6 864 0.50 0.54 14.2 Under 1 cu ft
12 x 12 x 8 1,152 0.67 0.72 18.9 Under 1 cu ft
12 x 12 x 10 1,440 0.83 0.89 23.6 Under 1 cu ft
12 x 12 x 12 1,728 1.00 1.06 28.3 Over 1 cu ft
13 x 13 x 13 2,197 1.27 1.35 36.0 Over 1 cu ft
14 x 10 x 8 1,120 0.65 0.70 18.4 Under 1 cu ft
14 x 10 x 10 1,400 0.81 0.87 22.9 Under 1 cu ft
14 x 12 x 10 1,680 0.97 1.04 27.5 Over 1 cu ft
14 x 14 x 8 1,568 0.91 0.97 25.7 Under 1 cu ft
14 x 14 x 14 2,744 1.59 1.67 45.0 Over 1 cu ft
15 x 12 x 10 1,800 1.04 1.11 29.5 Over 1 cu ft
16 x 10 x 6 960 0.56 0.60 15.7 Under 1 cu ft
16 x 12 x 6 1,152 0.67 0.72 18.9 Under 1 cu ft
16 x 12 x 8 1,536 0.89 0.95 25.2 Under 1 cu ft
16 x 12 x 12 2,304 1.33 1.41 37.8 Over 1 cu ft
16 x 16 x 8 2,048 1.19 1.26 33.6 Over 1 cu ft
16 x 16 x 16 4,096 2.37 2.48 67.1 Over 2 cu ft
17 x 11 x 11 2,057 1.19 1.26 33.7 Over 1 cu ft
18 x 12 x 6 1,296 0.75 0.81 21.2 Under 1 cu ft
18 x 12 x 12 2,592 1.50 1.58 42.5 Over 1 cu ft
18 x 14 x 12 3,024 1.75 1.84 49.6 Over 1 cu ft
18 x 18 x 12 3,888 2.25 2.36 63.7 Over 2 cu ft
18 x 18 x 18 5,832 3.38 3.52 95.6 Over 2 cu ft
20 x 14 x 10 2,800 1.62 1.71 45.9 Over 1 cu ft
20 x 16 x 12 3,840 2.22 2.33 62.9 Over 2 cu ft
20 x 20 x 12 4,800 2.78 2.91 78.7 Over 2 cu ft
20 x 20 x 20 8,000 4.63 4.81 131.1 Over 2 cu ft
22 x 22 x 22 10,648 6.16 6.37 174.5 Over 2 cu ft
24 x 12 x 12 3,456 2.00 2.11 56.6 Over 2 cu ft
24 x 18 x 12 5,184 3.00 3.14 85.0 Over 2 cu ft
24 x 18 x 18 7,776 4.50 4.67 127.4 Over 2 cu ft
24 x 24 x 12 6,912 4.00 4.17 113.3 Over 2 cu ft
24 x 24 x 18 10,368 6.00 6.21 169.9 Over 2 cu ft
24 x 24 x 24 13,824 8.00 8.25 226.5 Over 2 cu ft
26 x 20 x 14 7,280 4.21 4.38 119.3 Over 2 cu ft
28 x 20 x 16 8,960 5.19 5.38 146.8 Over 2 cu ft
30 x 20 x 20 12,000 6.94 7.18 196.6 Over 2 cu ft
36 x 24 x 24 20,736 12.00 12.34 339.8 Over 2 cu ft

11 of the 60 sizes sit between 1 and 2 cubic feet outside, and 17 exceed 2 cubic feet. The sizes just under 1 cubic foot, such as 14 x 10 x 10, 16 x 12 x 8 and 12 x 12 x 10, are the ones worth standardizing on for USPS Ground Advantage because they take actual weight pricing with no volume fee. The dimensional weight chart converts every size above into billable pounds at divisor 139.

Unit conversions

Unit Equals
1 cubic foot 1,728 cubic inches; 28.32 liters; 7.48 US gallons; 0.0283 cubic meters
1 cubic inch 16.39 cubic centimeters; 0.0164 liters
1 liter 61.02 cubic inches; 0.0353 cubic feet
1 cubic meter 35.31 cubic feet; 61,024 cubic inches
1 US gallon 231 cubic inches; 0.134 cubic feet; 3.785 liters

Finding a box by volume

Moving, storage and freight quotes are often written in cubic feet rather than box dimensions. The table picks the stocked sizes nearest to each common target so a 1 cubic foot spec or a 3 cubic foot spec can be filled from stock. Where two sizes have the same volume, the one closer to a cube has the most stacking strength per unit of board and the lowest length plus girth.

Target volume Stocked sizes closest to it
About 1/4 cu ft 12 x 6 x 6 (0.25 cu ft), 8 x 8 x 6 (0.22 cu ft), 10 x 8 x 6 (0.28 cu ft)
About 1/2 cu ft 12 x 12 x 6 (0.50 cu ft), 10 x 10 x 8 (0.46 cu ft), 12 x 10 x 8 (0.56 cu ft)
About 1 cu ft 12 x 12 x 12 (1.00 cu ft), 14 x 12 x 10 (0.97 cu ft), 15 x 12 x 10 (1.04 cu ft)
About 1 1/2 cu ft 18 x 12 x 12 (1.50 cu ft), 14 x 14 x 14 (1.59 cu ft), 20 x 14 x 10 (1.62 cu ft)
About 2 cu ft 24 x 12 x 12 (2.00 cu ft), 20 x 16 x 12 (2.22 cu ft), 18 x 14 x 12 (1.75 cu ft)
About 3 cu ft 24 x 18 x 12 (3.00 cu ft), 20 x 20 x 12 (2.78 cu ft), 18 x 18 x 18 (3.38 cu ft)
About 4 cu ft 24 x 24 x 12 (4.00 cu ft), 26 x 20 x 14 (4.21 cu ft), 24 x 18 x 18 (4.50 cu ft)
About 6 cu ft 24 x 24 x 18 (6.00 cu ft), 22 x 22 x 22 (6.16 cu ft), 28 x 20 x 16 (5.19 cu ft)
About 8 cu ft 24 x 24 x 24 (8.00 cu ft), 30 x 20 x 20 (6.94 cu ft)
About 12 cu ft 36 x 24 x 24 (12.00 cu ft)

Three places cubic feet shows up

  • Carrier pricing. USPS uses the 1 and 2 cubic foot lines above. UPS and FedEx use cubic inches through dimensional weight, and from January 2026 UPS treats cubic volume over 17,280 cubic inches (10 cubic feet) as a Large Package. The carrier limits page lists every threshold.
  • Freight and storage. LTL class is partly density (weight per cubic foot of the packed shipment), and warehouse storage is billed per cubic foot or per pallet position. A 48 x 40 pallet loaded 48 inches high is 53.3 cubic feet; the pallet table shows how many of each box size reach that height.
  • Moving estimates. Movers quote by cubic feet of load. A 'medium' moving box is conventionally 3 cubic feet (18 x 18 x 16 is 3.0), a 'large' 4.5 cubic feet (18 x 18 x 24 is 4.5), and a 'small' 1.5 cubic feet (16 x 12 x 12 is 1.33; 17 x 11 x 11 is 1.19).

For the same sizes in metric, the box sizes in cm page lists centimeters, millimeters and liters side by side.

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Frequently asked questions

How many cubic feet is a 12x12x12 box?

Exactly 1 cubic foot inside (1,728 cubic inches). With single wall board the outside is about 12.25 inches per side, or 1.06 cubic feet, which puts it just over the USPS 1 cubic foot dimensional weight line.

How do I calculate the cubic feet of a box?

Length x width x height in inches, divided by 1,728. For centimeters, multiply the three dimensions and divide by 28,317. The result is inside volume if you use inside dimensions.

How many cubic feet is an 18x18x18 box?

3.375 cubic feet inside (5,832 cubic inches), about 95.6 liters. Outside it is roughly 3.5 cubic feet, so it pays USPS dimensional weight and the nonstandard volume fee for exceeding 2 cubic feet.

Does USPS charge by cubic feet?

Partly. Parcels over 1 cubic foot are priced on dimensional weight (cubic inches divided by 139) when that exceeds actual weight, and parcels over 2 cubic feet pay a nonstandard fee on top. Under 1 cubic foot, only actual weight counts.

What box is 2 cubic feet?

24 x 12 x 12 is exactly 2.0 cubic feet inside and 20 x 16 x 12 is 2.22. To stay under the USPS 2 cubic foot nonstandard line on outside measurement, 18 x 14 x 12 is 1.75 inside and 1.84 outside.

Related references