Void Fill, Cushioning and Dunnage: A Practical Packing Guide

Why the Three Terms Get Confused

Carrier general packaging guidance gives concrete starting points. UPS calls for at least 2 inches of appropriate cushioning between items and between items and the corners, sides, top and bottom of the container. FedEx calls for a minimum 3 inches of air-cellular cushioning for fragile products shipped individually. Its double-boxing steps specify at least 2 inches of air-cellular cushioning or foam around the product inside the inner box, then 3 inches of cushioning around the inner box. FedEx also specifies an outer box at least 6 inches longer, wider and deeper. When selecting actual boxes, compare the inner box's exterior dimensions with the outer box's usable interior dimensions to confirm the required clearance.

These are recommendations from the cited carrier guides, not universal specifications or performance guarantees. Heavier, denser or more fragile goods may need engineered foam, suspension or crating. We recommend selecting and testing the packaging for the product and expected distribution environment.

• Void fill: occupies empty space to limit movement; fragile products may also need dedicated cushioning.
• Cushioning: helps protect against impact through wraps, pads, inserts or other structures; the cited carrier guides give thickness recommendations for particular packing methods.
• Dunnage: a broad term for materials that support, separate or secure cargo, often used in pallet and freight packing; it can overlap with void fill and cushioning.

Double-Boxing Fragile Items, Step by Step

This table is Teal Packaging's editorial planning framework for matching materials to jobs. The carrier sources cited below support only the specific cushioning thicknesses and double-boxing dimensions mentioned, not the material comparisons.

• Hypothetical inner box: exterior dimensions of 6 by 6 by 8 inches, with enough usable interior space for the product and its selected cushioning.
• Hypothetical outer box: usable interior dimensions of 12 by 12 by 14 inches. A centered inner box with exterior dimensions of 6 by 6 by 8 inches leaves 3 inches of clearance on each face. Confirm actual fit and cushioning thickness; the outer box's exterior dimensions will be larger.
• Separate hypothetical dimensional-weight example: a shipping package with exterior dimensions of 12 by 12 by 14 inches has a volume of 2,016 cubic inches. Dividing by the cited FedEx divisor of 139 gives about 14.5 pounds before applicable rounding. This is not the exterior size of the nested-box example above. Confirm the service's measurement, rounding and divisor rules, then compare dimensional weight with actual weight.

Box Strength and Weight Limits

Cushioning cannot compensate for an under-rated box. UPS publishes box strength guidance by weight: for example, single-wall boxes are listed for loads up to 80 pounds depending on size and board grade, while loads from 81 to 150 pounds call for double-wall construction with higher bursting or edge crush values. Never exceed the maximum gross weight printed on the Box Maker's Certificate on the bottom flap of the box. Avoid reusing boxes for freight shipments, and inspect any box for tears, corner dents or punctured flaps before packing.

The size limits in the UPS box strength chart describe the maximum box size that can be manufactured from a given board strength. They are unrelated to the length-and-girth measurements UPS uses for dimensional measurements.

• Check the Box Maker's Certificate for the maximum gross weight.
• Match wall construction to total packed weight, not product weight alone.
• Double-wall boxes for heavier items are a standard carrier recommendation.

Liquids, Glass and Irregular Shapes

Bottles containing liquids should be positioned upright, with an inner seal and a perforated breakaway cap, and inner packaging that can contain leaks. For framed glass, apply masking tape in a criss-cross pattern on the surface to help prevent splintering. For odd or irregular-shaped items, at minimum wrap and tape all sharp edges and protrusions. Chipboard gift or shoe boxes must be packed inside a corrugated outer box. Enclose an extra label or card with shipper and recipient contact details inside the package in case the outer label is damaged.

• Upright orientation, inner seal and leak-containing inner packaging for liquids.
• Criss-cross masking tape on glass surfaces.
• Wrap and tape all sharp edges and protrusions on irregular items.

Balancing Dimensional Weight and Cushioning

FedEx calculates dimensional weight by multiplying length by width by height in inches and dividing by 139 for U.S., Puerto Rico and international shipments. Other carriers and negotiated agreements may use different divisors. Chargeable weight is the greater of actual or dimensional weight, so extra cushioning adds billable volume when a package is light relative to its size. We recommend using the minimum cushioning thickness that genuinely protects the product, choosing a box that fits that cushioning without large leftover voids, and avoiding oversized boxes that inflate shipping cost.

• Calculate dimensional weight before committing to a box size.
• Use the smallest box that still allows the required cushioning thickness.
• Fill remaining voids so the product cannot shift, as carrier guidance recommends.

Ecommerce Channel Considerations

Some channels, such as Amazon's Ships in Product Packaging program for FBA sellers, allow products to ship without channel-added protective material, which can lower fulfillment costs. Enrollment involves eligibility checks, grouping products by size, weight, material and product-to-packaging ratio, and testing. Products under 50 pounds without liquids or sharp items may be self-tested, while others may need a third-party ISTA 6 lab test. Confirm current program requirements, discounts and eligibility in your own seller agreement, since these details can change and this guide does not reproduce them in full.

This is a different design problem from parcel packing. The product packaging itself must pass the program's testing, so design decisions should be validated against those requirements rather than assumed from generic void fill practice.

• Program-based shipping in product packaging typically requires certification testing.
• Self-testing may be limited to lighter products without liquids or sharp items.
• Confirm channel rules in your own agreement rather than relying on third-party summaries.

Pre-Ship Checklist

Run through this list before sealing any protective package. It reflects Teal Packaging's editorial planning framework combined with carrier packing principles.

• Box strength matches total packed weight and the Box Maker's Certificate limit.
• Check the applicable carrier guidance: FedEx recommends at least 3 inches of air-cellular cushioning for individually shipped fragile products; UPS recommends at least 2 inches of appropriate cushioning between items and container surfaces.
• For the cited FedEx double-boxing method, wrap the product in at least 2 inches of air-cellular cushioning or foam inside the inner box, then provide 3 inches of cushioning around that box. Check that the outer box provides the necessary usable interior clearance.
• A gentle movement check reveals no obvious shifting; this check does not establish transit performance.
• Liquids upright with inner seals and leak-containing inner packaging.
• Sharp edges and protrusions wrapped and taped.
• Old labels removed; box free of tears, dents and holes.
• H taping applied; as a recommendation, place the label on a flat top surface away from seams.
• Extra label or contact card enclosed inside.

Scope and Limits

This guide focuses on general parcel packing, with introductory freight considerations rather than a freight load-securement specification. It does not cover hazardous materials, cold chain, regulated food contact or child-resistant packaging; review applicable requirements with the appropriate authority or qualified advisor. Cushioning thicknesses and double-boxing dimensions here are carrier guidelines, not performance guarantees. Actual protection depends on the product, material and distribution environment. For fragile, heavy or high-value goods, we recommend a test plan suited to the expected hazards, with defined acceptance criteria. An informal drop test or transit trial can inform development but does not by itself establish adequate protection. Dimensional-weight arithmetic is not evidence of protective performance.

Questions about void fill, cushioning and dunnage