Calculate shipping box size: the optimal box for your products
The right box size is an underrated cost factor: boxes that are too big cost postage, filling material and licensing fees, while boxes that are too small put the product at risk. Since the PPWR, the 40% void-space limit adds to this — box size becomes a compliance question.
As a rule of thumb, the box's internal volume should exceed the product volume by no more than roughly two thirds so that void space stays below 40%. For irregularly shaped products, plan a protective margin without needlessly enlarging the box.
The PPWR void-space calculator computes the void-space ratio from product and box dimensions and, if there is too much air, recommends a concrete, smaller box height.
Your checklist
- 1Capture product dimensions: measure the length, width and height of the product (or all items in the parcel).
- 2Set a protective margin: plan an appropriate buffer depending on fragility — as little as possible.
- 3Choose the box size: take the smallest standard size that fits the product plus the protective margin.
- 4Check the void space: verify the ratio against the 40% limit and pick a flatter size if needed.
- 5Design the range: keep several tiered box sizes so different products have a suitable fit.
Matching tool
Stay within the PPWR's 40% void-space limit.
PPWR Void-Space Calculator → Check now for freeFrequently asked questions
Which box size saves postage?
The smallest size that safely fits your product. Many carriers charge by size/weight — compact boxes save postage directly while staying within the PPWR void-space limit.
How many box sizes should I stock?
Enough to cover your range with as little void space as possible. In practice, five to ten tiered sizes often suffice; height-adjustable boxes reduce the number needed.