Nobody publishes the number that matters most for a return leg: how many empties fit in the vehicle you actually run. Suppliers publish nested height, which is not the same thing, because nested height assumes perfect nesting and a vehicle is not a perfect cuboid. The good news is that the real number takes ten minutes to measure and removes the guesswork from the business case.
Measure the stack, not the box
Take ten empty boxes, stack or nest them the way they will actually travel – which usually means the way a tired person would do it, not the way the drawing shows – and measure the total height. Divide by ten and you have an effective height per empty box, including the slop that never appears on a spec sheet. Do it three times with three different people and take the worst, because the worst is what you will get on a Friday.
Then measure the usable cube
Vehicle internal dimensions are published and almost always optimistic: wheel arches, a sloping roof, a bulkhead and a door aperture that is smaller than the opening all reduce usable volume. Measure the door aperture height first, because that is the hard limit on how tall a stack can be loaded, then the usable width at floor level, then the usable length. Multiply and you have a usable cube that is usually fifteen to twenty per cent below the brochure figure.
Loading pattern beats arithmetic
Boxes do not fill a cube perfectly. A stack of empties turned alternately fills a rectangular load better than a single orientation, and leaving turning clearance out of the estimate is how plans fail at the tail lift. A conservative packing efficiency for stacked empties is around eighty per cent of usable cube; below seventy if the boxes are large or the vehicle is small. Apply it and stop arguing about it. The equivalent calculation for a flat product is laid out in how many panels fit in a forty-foot container. The equivalent calculation for a flat product is laid out in how many panels fit in a forty-foot container.
The number to put in the business case
Empties per vehicle run, times return runs per week, times cost per run. Compare that against the same calculation for a nestable or collapsible alternative and the difference is the annual return cost. On a two-hundred-kilometre return leg run twice a week, the difference between a box that nests three to one and one that does not nest at all is usually a four-figure annual number, and it is often larger than the difference in unit price that decided the original purchase.
Why the last ten per cent costs so much
Loading empties has a brutal tail. The first eighty per cent of a vehicle fills quickly and tidily. The last twenty per cent is a fight with the door aperture, the wheel arches and the fact that the boxes do not quite tile the remaining space. Teams that plan to a theoretical cube spend an extra forty minutes at the dock every run, and the saving from a better nesting ratio gets eaten by loading labour.
The practical answer is to plan to a realistic figure rather than a theoretical one and stop when the vehicle is comfortably full. If the arithmetic says four hundred empties and the reality is three hundred and fifty in reasonable time, plan for three hundred and fifty and accept one extra run a month. Alternatively, change the loading method: empties loaded in blocks on a pallet, strapped, and put in with a pump truck go in faster and more densely than hand-loaded stacks, and the pallet cost is trivial against forty minutes of a driver and a mate on every run.
What we can do
We build PP corrugated turnover boxes and will quote effective empty height per ten boxes rather than a theoretical nested height. Tell us the vehicle and the return frequency and we will give you empties per run as a real number, measured the way your team would load it.