Why You Need Twice as Many Small Boxes as Medium Ones

The first thing people notice in a box estimate is that the small-box number is enormous. It looks like an error, and every instinct says to order fewer small boxes and more large ones.

It is not an error, and following the instinct is how a move ends with boxes nobody can lift.

Where the numbers come from

A bedroom is 45 cubic feet of boxable belongings. The estimator splits that by volume — 40% into small boxes, 40% into medium, 20% into large — and then divides each share by that box's capacity.

Box	Holds	Share of volume	How many	Share of count
Small	1.5 cu ft	40%	12	60%
Medium	3 cu ft	40%	6	30%
Large	4.5 cu ft	20%	2	10%

Small and medium take the same share of the volume and a small box holds half what a medium one does, so you need twice as many. The count follows from the capacity, not from anybody's preference.

Why not just use large boxes

You could. 45 cubic feet in large boxes alone is 10 boxes against 20 — half the count, and an obvious win on paper.

It fails on weight. A large box holds 4.5 cubic feet, and 4.5 cubic feet of books is far past what one person should carry. The box sizes are not about volume efficiency at all; they are about keeping the loaded weight of each box within human range, and that means dense things go in small boxes.

The rule movers use: heavy things in small boxes, light things in large ones. The distribution in the estimator is that rule turned into arithmetic.

And the reverse

All small boxes would be 30 of them — 10 more than the mixed answer, every one of which has to be labelled, carried, stacked and unpacked separately.

Duvets in small boxes is its own kind of absurd. Light bulky things want large boxes precisely because the weight will never be the constraint.

What goes in which

Small: books, records, tinned food, tools, crockery, anything metal. If a shelf of it would be heavy, it goes in a small box.

Medium: the default. Kitchen items, toys, small appliances, shoes, most of what a house actually contains.

Large: bedding, cushions, coats, lampshades, empty luggage. Things that fill a box without loading it.

Applied honestly, this produces roughly the split the estimator predicts — which is the point of the split, rather than a coincidence.

Rounding is per size, and it adds up

Each size is rounded up separately, so a small home ends up with a box or two of slack in each category. Across 20 boxes that is a few per cent, and it is the right direction to err in.

Across a whole flat the same rounding is still only a handful of boxes, which is worth knowing if you are comparing the estimator's answer against a removal firm's — a firm quoting materially fewer boxes is quoting for a different amount of stuff, not a cleverer arrangement.

The weight nobody estimates

Volume is what the tool models. Weight is what your back experiences, and the two diverge most sharply in the kitchen, which is both the densest room and the one people pack last and fastest.

A practical ceiling is about 40 pounds a box. Above that, two people are needed and stacking becomes unsafe — and a box you cannot lift onto another box is a box that will sit in the middle of a room for a week.

Ordering, in one line

Take the estimator's totals, add about fifteen per cent, and keep the ratio it gave you. The ratio is the part that is actually derived from something; the total is a typical figure you should expect to adjust.

And buy more tape than you think. Tape is the only consumable in a move that is never over-ordered and is reliably the thing someone drives out for at ten at night.

Packing to the ratio, not just to the total

The ratio only holds if the contents go in the right sizes, which means sorting by density before sorting by room.

The practical version: keep all three sizes open at once and choose per item rather than per shelf. Packing a bookshelf into whatever box is nearest is how a move ends with 2 large boxes of books and nobody willing to carry them.

Labelling is part of the arithmetic

20 boxes from one bedroom is already past what anyone can remember. Write the room and two or three contents words on the side, not the top — stacked boxes hide their tops — and mark the ones to open first.

The payoff is at the other end. A move is unpacked in the order the labels allow, and unlabelled boxes get opened last, which is how a kitchen stays in cardboard for a fortnight.

Why the estimator does not just ask for a weight

Because nobody knows what their belongings weigh, and everybody can look at a room. Volume is the only input a person can supply honestly, which is why every box estimate in existence is built on cubic feet.

The box sizes are how weight gets back into the answer. A three-way split by volume, with capacities chosen so that a full box of the appropriate contents lands in liftable range, is a weight model wearing a volume model's clothes — and it works because the contents that are dense are also the contents that are small.

The check worth doing at the end

Count your filled boxes by size and compare the ratio to the plan. A big surplus of large boxes means light things went in small ones; a shortage means heavy things went in large ones, and the second is the one that hurts on moving day.

It takes a minute and it is the only feedback the estimate ever gets — which is worth having before the next move rather than after it.