Choosing cushioning by product weight and fragility
Match protection to the product: judge fragility, weight and contact area, then choose cushioning, void fill or blocking. With a simple decision table.
"Should I use bubble wrap, air pillows or paper?"
It is probably the most common question in protective packaging, and it cannot be answered on its own. Two more questions come first. How fragile is the product? And how heavy is it, for the area it rests on?
We make air cushions and paper cushioning, so I will try to answer it fairly, including the jobs where our own materials are the wrong choice.
Start with the product, not the material.
Judge how fragile it is, note its weight and its contact area, and decide which job the packing must do: soften a knock, fill empty space, or hold the product in one place. Then pick a material that does that job at that weight. This guide walks through each step and ends with a decision table you can use on your packing table.
Cushioning, void fill and blocking are three different jobs
Many packing mistakes come from mixing these up, so I will keep them apart for the rest of this guide.
- Cushioning softens a knock. When the box hits the floor, the cushion squashes and springs back, so the product slows down over a few millimetres instead of stopping dead. Bubble wrap, air column bags, foam and paper wraps such as honeycomb paper do this job.
- Void fill takes up empty space, so the product cannot slide around and hit the walls. Air pillows, crumpled paper and loose fill do this job.
- Blocking and bracing hold the product in one fixed position, usually away from the walls. Corrugated inserts, moulded pulp trays and foam end caps do this job.
There is a fourth, smaller job: surface protection. A sheet of tissue or thin paper stops scratches on a glossy finish. It is not a cushion.
The common mistake is to use void fill as if it were cushioning. UPS's own Packaging Guidelines (PDF, November 2024) describe air bags and crumpled kraft paper as mainly void fill for lightweight items, and say air bags are not recommended for items with sharp corners or edges.
Pillows around a heavy glass bottle keep it in place. They are not built to take a hard knock for it.
How fragile is your product?
Fragility is the size of knock a product can take before it breaks or stops working. Laboratories measure it on a shock machine and express it in "g", multiples of the pull of gravity. The method is ASTM D3332 (D3332-99, reapproved 2023), which finds the change in speed and the peak deceleration a product can take before it is damaged.
Most small sellers do not need a lab number. ISTA's overview of its parcel test 3A (2018) uses a plain definition instead: fragile products are items that could easily break if dropped without protective packaging, such as glass, ceramics, porcelain, clay and electronics. Sorting your own products into four groups is enough to start:
- Sturdy: clothes, books, steel utensils, most plastic toys. Damage is mostly dents and scuffs.
- Moderately fragile: products already in their own retail carton, plastic bottles, packaged foods, small appliances.
- Fragile: glass, ceramics, cosmetics in glass, anything with a screen.
- Very fragile: large glass, mirrors, framed art, precision instruments, anything with long thin parts.
I would add two warnings.
First, the weakest part decides, not the average. A sturdy kettle with a thin plastic handle is only as strong as the handle. Second, some products do not break, they just stop working. Electronics can look perfect after a knock and still fail when switched on. For those, check function, not just looks.
Why weight and contact area matter
Stand on a soft mattress in flat chappals, then in high heels. Your weight is the same both times, but the heels sink much deeper, because the same weight now presses on a much smaller area.
Cushions behave the same way. A cushion only works if it squashes part of the way, and no further.
- A heavy product on a small contact area, like a cast-iron kadai resting on its rim or a small machine on its feet, presses hard into the cushion and goes right through it. The cushion bottoms out and the shock reaches the product. Use a firmer or thicker cushion, or spread the load first with a flat corrugated pad under the product. Packaging engineers call this a load spreader.
- A light product on a large, stiff cushion hardly squashes it at all. The cushion then behaves almost like the box wall. Use something softer.
Packaging engineers call weight divided by the bearing area the "static stress", or static loading. The US Department of Defense handbook on cushion design, MIL-HDBK-304C (1 June 1997), builds its whole method on curves of peak acceleration against static stress, one curve for each cushion thickness and drop height. Those curves come from drop tests such as ASTM D1596 (D1596-14, reapproved 2023).
ASTM itself cautions that such lab data may not predict how a cushion behaves inside a real package. That is one more reason to test your own pack. If you are buying engineered foam for one product, ask the supplier for the cushion curves at your static loading. A serious supplier will have them.
How much space should you leave?
UPS's guidelines ask for at least two inches (about 5 cm) of cushioning to protect items from each other and from the corners, sides, top and bottom of the box. For the two-box method, they suggest an outer box 6 inches (about 15 cm) bigger than the inner box in each dimension, with 3 inches (about 7.5 cm) of cushioning around the inner box.
These are one courier's rules for its own network, not a law for every parcel. Still, they are a sensible place to start. For sturdy products you can test with less. For glass and ceramics, I would start at these figures and only cut back once a drop test says it is safe.
The options, on equal terms
We make the air and paper options in this table, so read it with that in mind. I have tried to give each one its honest weak point.
| Material | Main job | Good for | Weak at |
|---|---|---|---|
| Air pillows | Void fill | Filling gaps around light items quickly, at very little weight | Sharp corners, heavy loads, very hot or cold routes |
| Air column bags | Cushioning | Bottles, electronics and lamps, each wrapped in its own bag | Higher cost per parcel, and they need a pump or compressor |
| Bubble wrap | Cushioning and surface protection | Light and medium items, wrapped in several layers with the corners covered | Heavy point loads, and buyers who want a plastic-free box |
| Paper wraps (honeycomb, paper bubble) | Cushioning and surface protection | Light and medium items, gifts, glassware wrapped in layers | Wet conditions, and heavy items with sharp corners |
| Crumpled kraft or void fill paper | Void fill, and some blocking when packed tight | Filling gaps in plastic-free boxes | Heavy fragile items on its own, and loose packing that settles |
| Engineered foam | Cushioning and blocking | Heavy or very fragile items with a fixed shape | Storage space, made for one product, harder to recycle in many places |
| Corrugated or moulded pulp inserts | Blocking and bracing | Repeat products that must stay off the walls | Made for one product, so a new design for every new SKU |
If you are choosing between bubble grades, our guide to bubble wrap grades explains bubble size, height and film.
A decision table to start from
Weight here is described by how you lift it, not by an exact kilogram figure. Light means one hand. Medium means two hands. Heavy means you brace yourself before lifting.
| Product | Weight | Fragility | Main job | A starting set-up to test |
|---|---|---|---|---|
| Clothes, books, soft goods | Any | Low | Stop movement, keep dry | A right-sized box or mailer, with a little paper or a few pillows in the gaps |
| A product in its own retail carton | Light to medium | Low to medium | Void fill | Pillows or tightly crumpled paper around the carton |
| Glass jars, bottles, ceramics | Light to medium | High | Cushion every side, keep items apart | Wrap in bubble, honeycomb paper or air columns, then fill the gaps, with dividers for more than one item |
| Electronics, anything with a screen | Light to medium | High, and damage may be hidden | Cushion and block | End caps or air columns, product held off the walls, nothing loose |
| Heavy items with hard corners (tools, cast iron, small machines) | Heavy | Low for breakage, high for puncture | Block, and protect the corners | Corrugated inserts or foam end caps, tightly packed paper, a stronger box. Never air pillows alone |
| Large glass, mirrors, art, precision instruments | Medium to heavy | Very high | Cushion plus rigid protection | Two boxes with corner protectors, or engineered foam. Consider a professional pack design or a crate |
Treat every row as a starting point, not an answer. Your product, your box and your courier will move it one way or the other.
Once you settle on a set-up for each group, I would write it on a card and stick it above the packing table, so every packer does it the same way.
Mistakes to avoid
I have put the one I would fix first at the top.
- Using void fill as the cushion for a heavy, fragile product.
- One thin layer of bubble around a heavy item. It bottoms out on the first hard knock.
- A box far bigger than the product, then filled with loose material that settles on the way.
- A heavy item and a fragile item in the same box with nothing between them.
- Very firm foam around a light product, so the foam never squashes and never cushions.
- Forgetting the weakest part: the handle, the spout, the corner of the screen.
Test it before you switch
A table can point you in the right direction. Only a test tells you whether it works for your product. Pack three boxes your current way and three the new way, and run a simple drop test in your own warehouse. Then watch your damage rate for a few weeks after the change.
If you are unsure where to start, send us the product's weight, a photo of it, and how it travels. We will suggest two set-ups you can test side by side.
Questions buyers ask
Can I use one cushioning set-up for every product?
You can, but you will over-protect light, sturdy items and under-protect heavy, fragile ones. Most sellers do well with two or three standard set-ups, one for each group of products, written down so every packer uses them the same way.
Is foam better than air or paper?
For heavy or very fragile products with a fixed shape, engineered foam often protects best, because it is made for that one product. It is bulky to store, it suits only that product, and it is harder to recycle in many places. For mixed orders, air and paper are easier to live with.
How do I know if my cushion is too thin?
Open the box after a drop test and look under the product. If the cushion is flattened right through where the product pressed on it, or the product touched the box wall, the cushion bottomed out. Use a thicker or firmer cushion and test again.