How to calculate cubic feet in Excel

Cubic feet from inches: divide by 1,728

A cubic foot is a box 12 inches on each side, so it holds 12 x 12 x 12 = 1,728 cubic inches. Box sizes are usually printed in inches, so multiply the three sides and divide by 1,728. The divisor sits in I2 so the formulas show where it came from.

A medium moving box of 18 x 18 x 16 inches is 5,184 cubic inches, which is exactly 3 cubic feet. The small 16 x 12 x 12 box comes to 1.33. Format column F with two decimals. The full value is still there for the totals.

The common slip is dividing by 12 once. That turns inches into feet on one side only and gives an answer 144 times too big.

Total volume of a packing list

You're moving and need to know which truck to book. Each row has the size of one item and how many you have. SUMPRODUCT multiplies length x width x height x quantity row by row and adds the results, so you don't need a helper column at all: 164,128 cubic inches, or 94.98 cubic feet.

If you'd rather see each line, =F2*E2 in a new column and a SUM at the bottom gives the same total. Don't round each line first and then add. Here that gives 94.97, and on a long list the rounding piles up.

Then compare it with the truck. Boxes don't fill a space perfectly, and furniture leaves gaps, so put your own guess of how much you can really fill in I6. At 75% a 400 cubic foot truck holds about 300, and this list uses 31.7% of that. Plenty of room for the stuff you forgot to measure.

Feet and inches, and measuring rooms

For rooms, sheds or storage units you'll usually measure in feet. Then length x width x height is the answer: a 12 x 10 room with an 8-foot ceiling is 960 cubic feet. Don't divide by 1,728 here, that's only for inches.

Tape measures give feet and inches, like 12' 6". Turn the inches into a decimal of a foot by dividing by 12: 12 + 6/12 = 12.5. Typing 12.6 instead is a sneaky mistake, because 6 inches is half a foot, not 0.6 of one.

Pick one unit for the whole sheet and write it in the header ("Length in", "Length ft"). Mixed units in one column are the most common reason a volume comes out wildly wrong.

Cubic metres (CBM) for freight

Freight forwarders and overseas suppliers quote by the cubic metre (CBM). One cubic metre is about 35.3147 cubic feet, so divide the cubic feet by I4: this packing list is about 2.69 m³.

If you measured in centimetres, multiply the three sides and divide by 1,000,000 (100 x 100 x 100). A 60 x 40 x 40 cm carton is 96,000 cm³, or 0.096 m³. Couriers also use the volume to work out dimensional weight. Our shipping cost guide shows how that changes what you pay.

Excel also has a CONVERT function for units, for example =CONVERT(94.98,"ft3","m3"). A plain factor in a labeled cell is easier for the next person to check, and it works in every spreadsheet app.

Cubic feet to gallons (tanks, planters, ponds)

One cubic foot holds about 7.48052 US gallons. A 36 x 12 x 16 inch aquarium is 6,912 cubic inches, which is 4 cubic feet or about 29.92 gallons. You can also go straight from cubic inches, since a US gallon is 231 cubic inches: 6,912 / 231 is the same 29.92.

UK (imperial) gallons are bigger, about 277.42 cubic inches, so the same tank holds about 24.9 of those. Label which gallon you mean. For anything you fill, the inside measurements matter: glass and walls take up space, so measure inside if you need the exact amount.