How to Save on Shipping Costs by Optimising Postal Box Sizes
Cut shipping costs by matching postal box sizes to carrier pricing bands and product dimensions.
Why size matters for cost
Carriers charge by size as well as weight. An oversized, half-empty box costs more to ship than a right-sized box containing the same product. Dimensional weight pricing means you pay for the space your box occupies, not just what it weighs. Optimising box sizes is one of the easiest ways to reduce shipping costs.
Quick answer
Audit your product range, identify 3-5 box sizes that cover 90% of orders, and ensure each fits within the cheapest applicable carrier pricing band. Royal Mail's small parcel band (up to 61cm x 46cm x 46cm, 2kg) is significantly cheaper than medium parcel. Courier dimensional weight calculations penalise oversized boxes. Even reducing box height by 2cm can drop you into a cheaper band.
Carrier pricing bands
Keeping within 61cm x 46cm x 46cm saves significantly on every Royal Mail shipment.
The formula is typically L x W x H / 5000 (in cm). If dimensional weight exceeds actual weight, you pay the higher figure.
A box that is 1cm over a size threshold jumps to the next pricing band.
Size guidance: complete sizing guide or Royal Mail size guidelines.
Optimising your size range
Size optimisation steps0 / 5 checked
Size reduction strategies
Right-sized postal boxes
ProcuraPack offers postal boxes designed to fit Royal Mail and courier pricing bands for maximum savings.
Browse postal boxesFrequently asked questions
Carriers charge by size and weight. Oversized boxes incur dimensional weight charges higher than actual weight.
A pricing formula (L x W x H / 5000 in cm) that carriers use to charge for bulky but lightweight parcels.
Most businesses cover 90% of orders with 3-5 box sizes.
Yes, even 2cm less can drop you below a pricing threshold. Score lines let you adjust height.
Small parcel (up to 61cm x 46cm x 46cm, 2kg) is the cheapest parcel band.
Part of our guide
Product Guide: Postal Boxes
Expert guides on postal boxes, from sizing and materials to branding and cost optimisation.
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