Tare weight is the weight of the empty container. It is almost never the first thing considered in a packaging decision and it is frequently the most expensive. On a weight-limited lane, the box is being paid for at freight rates, trip after trip, for the whole life of the fleet.
The arithmetic
Take the tare weight per box, multiply by the number of boxes per load, and divide by the payload capacity. That is the fraction of the vehicle that is carrying packaging instead of product. On a dense part in a 24 tonne trailer the figure is often larger than anyone guessed.
Multiply by the fleet life
A box that weighs 1 kg more than it needs to and makes forty trips carries 40 kg of unnecessary weight per box position. Across a fleet of a few hundred boxes on a weekly lane, that is tonnes of freight a year. The board specification decision was made once and is paid for forever.
Where the weight sits
Mostly in the base, because the base is usually the thickest panel, and in any reinforcement – corner posts, feet, edge protection. Wall thickness is the small contributor. Where weight matters, the base is where to look first, and reinforcement is where the savings usually are.
The trade against strength
Less material means less stiffness and a lower stack rating. The trick is to keep material where it does structural work – vertical corners, load paths from the lid to the base – and remove it from flat panel areas where it does very little. That is a design change, not a specification change.
When tare weight does not matter
On volume-limited lanes, a heavier box that stacks one layer higher wins outright. In closed loops with a fixed number of boxes, tare weight is a one-off handling cost rather than a recurring freight cost. And for parts that are heavy relative to the box, the box weight is noise.
What to ask for
The tare weight of the box, the stack rating, and both figures for any alternative wall specification. Three numbers that let the trade be made explicitly rather than by default. A supplier with a range of board weights will have them to hand.
Where the weight actually is
Mostly the base, because it is the thickest panel, and then any reinforcement: corner posts, feet, edge protection. Wall thickness is usually the small contributor, which is why chasing thinner walls tends to disappoint. Where weight matters, ask which panel can be re-specified and what it does to the stack rating.
The trade is unavoidable. Less material means less stiffness and fewer permitted layers. The useful move is to keep material where it carries load – vertical corners, load paths from lid to base – and take it out of flat panel areas where it does very little.
How to check the real figure
Weigh a loaded box rather than taking the part weight from the drawing. The difference is dunnage, board and any internal fittings, and it is routinely ten per cent or more. Where the lane is weight-limited, that is the number the layer count and the payload both depend on.
What we can do
We build PP corrugated turnover boxes in a range of board weights and will quote tare weight against stack rating for each. Tell us the part weight and the mode, and we will show which one pays. Which of the two applies is explained in where the weight-versus-volume line sits. See also the companion piece, the two numbers belong side by side.