Moving boxes and carton volume

Two questions get asked at once when somebody starts packing: how much does this box actually hold, and how many of them am I going to need. Both have published answers, because moving is a regulated trade in some places and the regulator has to define what a carton is before it can price one. California's Maximum Rate Tariff 4 sets out six carton size classes in cubic feet and the weight each is assumed to carry when a claim is settled, and it tells estimators to multiply a shipment's total cubic feet by seven to get its approximate weight in pounds. This page uses those figures rather than the numbers a box shop puts on a website, so the class your carton falls in is the class a mover would put it in.

How it is calculated

cu ft = L × W × H ÷ 1728 · cartons = ⌈move ÷ carton⌉ · lb = move × 7

A cubic foot is 12 inches cubed, so a carton measured in inches gives up its volume for one division by 1728. The size classes are read off that volume: under 1½ cu ft, 1½ to under 3, 3 to under 4½, 4½ to under 6, 6 to under 6½, and 6½ and over, and the tariff assumes 20, 25, 30, 35, 45 and 50 pounds respectively when it has to settle a claim on a carton whose contents nobody wrote down. The seven pounds per cubic foot is the tariff's own instruction for estimating a shipment's weight, and it applies to the whole load rather than to boxes alone.

Source: Maximum Rate Tariff 4, Bureau of Household Goods and Services, California Department of Consumer Affairs, effective January 1, 2023 — Item 92, section 13, Constructive Weight of Packed Interior Shipping Containers — "in the absence of specific evidence to the contrary, such interior shipping container will be deemed to have the following weight", weight per container in pounds: cartons less than 1½ cu. ft. 20, 1½ - less than 3 cu. ft. 25, 3 - less than 4½ cu. ft. 30, 4½ - less than 6 cu. ft. 35, 6 - less than 6½ cu. ft. 45, 6½ cu. ft and over 50; NOTE 1: "Cartons containing books or phonograph records will be deemed to weigh 50 pounds."

Questions people ask

How do I work out the cubic feet of my move?

Add up your furniture from a published measurement table rather than guessing at the total. The tariff makes estimators use its own figures and gives them piece by piece: a double bed with spring and mattress is 60 cu ft, a king 70, a single 40; a dresser or chest of drawers is 25; a washing machine 25; an electric or gas range 30; a refrigerator of 7 to 10 cubic feet capacity is 45; a dish pack is 10 and a wardrobe carton 15. Those seven items alone come to 210 cu ft, which the seven-pounds rule turns into 1,470 lb.

Why does the tariff assume a weight for a box?

Because a claim has to be settled somehow when a box goes missing and nobody wrote down what was in it. The rule is called constructive weight, and it applies "in the absence of specific evidence to the contrary". It is a useful sanity check while you are packing, in the other direction: if a 3 cu ft carton is meant to come in around 30 lb and yours is at 60, you have put books in a box that was not meant to hold them. The tariff has a line for that too — cartons of books are deemed to weigh 50 lb whatever their size.

Is the box count exact?

No, and it cannot be. It divides your total by the volume of one carton and rounds up, which assumes boxes pack perfectly and that everything you own goes in a box. Neither is true: furniture, mattresses, bicycles and lamps are counted as themselves in the same measurement table, and a kitchen packs far less densely than a bookshelf. Treat the figure as the count for the boxable part of the move and buy a few more than it says.

Why cubic feet and inches rather than metric?

Because the source is a United States tariff and its classes are defined in cubic feet — 1½, 3, 4½, 6 and 6½. Converting the class boundaries to litres would produce numbers that look precise and match nothing any mover uses. If you are working in centimetres, convert the carton's sides to inches first and the classes stay the ones a mover would recognise.

Does this tariff apply where I live?

Almost certainly not as law. Maximum Rate Tariff 4 is issued by the Bureau of Household Goods and Services of the California Department of Consumer Affairs and governs moves inside California. It is used here because it is a published, freely readable document that defines carton classes and a weight rule in plain terms, not because it binds your mover. Your own mover's tariff may set the boundaries differently, and if you are comparing quotes, that document is the one to read.

Related tools