Key takeaways
- Cost per trip = (unit price + freight per unit − residual value) ÷ effective trips. Most buyers track only one of the four inputs.
- Effective trips is a divisor, so it has the most leverage and is the input hardest to find out.
- A cheap box that survives one trip can cost more per trip than a pricier box that survives several.
- If nobody will take a container back at the end of its life, residual value is negative, because disposal costs money.
Almost every packaging purchase is evaluated on unit price, because unit price is the number on the invoice and the number in the purchasing system. In reusable packaging it is also close to meaningless on its own.
The formula
Cost per trip = (unit price + freight per unit − residual value) ÷ effective trips achieved.
Four inputs. Most buyers track one.
Unit price
The easy one, and the one everybody optimises. It usually makes up the largest share of the answer and gets by far the most attention.
Freight per unit
Large for bulky, low-value goods. Whether a box travels flattened or assembled changes this enormously, and so does whether a return load is available on your route. A box that is slightly cheaper but ships assembled is often not cheaper at all.
Residual value
What the container is worth when you have finished with it. If someone will buy used boxes from you, it is a positive number. If nobody will, it is negative, because disposal costs money.
Effective trips
How many journeys you actually get, after damage and losses. This is the input nobody measures and the one with the largest leverage, because it is a divisor.
| Input | What it covers | Common blind spot |
|---|---|---|
| Unit price | The invoice price of the box | Gets all the attention and ignores the rest |
| Freight per unit | Delivery, handling and the space a box takes on the truck | Assembled versus flattened, and return loads |
| Residual value | What the box is worth, or costs, at end of life | Assumed to be nothing when it is often a cost |
| Effective trips | Real journeys after damage and loss | Rarely measured, so rarely questioned |
A simple illustration
Take two boxes with hypothetical, round numbers. Box A costs 10 units delivered and survives five trips: 2 per trip. Box B costs 6 units delivered but is only good for two trips: 3 per trip. On unit price, Box B wins easily. On cost per trip, it is the more expensive choice. That inversion is the entire point of the metric.
When the cheap box genuinely wins
When effective trips is one whatever you buy. One-way outbound shipments, processes that destroy containers on discharge, and material that goes to a customer and never returns. In those cases durability is wasted and the cheapest container that gets the load there intact is the right one.
That is why well-run operations often use two grades: a better one for loops that return, a more economical one for one-way flows. Few do, because purchasing systems dislike two part numbers for the same thing.
Getting the trips number
Mark a sample of boxes with a paint pen and record weekly how many are still in service. A few minutes a week over a couple of months is enough. It is the only way to get a reliable figure, since no supplier can tell you how your own handling treats a box, and many people who do this find the real number is below their assumption.
The line that usually gets missed
Residual value. Ask any supplier whether anyone will take containers back at the end of their life. If the answer is no, that line is not nothing: it is negative by whatever your disposal costs, including compactor pulls and handling, apportioned per box.
If you want help comparing options, send a free, no-obligation quote request describing your boxes and flows and a partner supplier can follow up with what is available.
Questions