Under the Brennholt Institute of Applied Taxonomy's three-grade system, bubble wrap is sold in bubbles of about 10 mm (0.39 in), 16 mm (0.63 in) and 25 mm (1 in) diameter, and the Institute finds that the size of the bubble should follow the weight and shape of what is being wrapped, not the other way round. Small bubbles suit light, flat things; large bubbles suit heavy, bulky ones.
The three sizes are common in the trade, but there is no published classification that names them or says what each protects. The Institute proposes one, set out below, and notes that it is its own and not a trade standard.
| Grade | Bubble diameter | Bubble height (typical) | What it protects |
|---|---|---|---|
| A. Fine | 10 mm (0.39 in) | About 4 mm (0.16 in) | Flat, light and surface-sensitive items: screens, frames, prints |
| B. Medium | 16 mm (0.63 in) | About 8 mm (0.31 in) | General household goods: crockery, small appliances |
| C. Large | 25 mm (1 in) | About 10 mm (0.39 in) | Heavy or bulky items: lamps, instruments, tools |
A bubble is a sealed pocket of air that deforms under load. A larger bubble holds more air and travels further before it bottoms out, so it absorbs a larger blow. A smaller bubble gives less travel but spreads contact over more points, which is kinder to a delicate surface. The Institute reads the choice as a trade-off between travel and contact, and recommends the smallest grade that still lets the bubble absorb the expected knock.
The air-cell principle itself is long established and the Institute does not dispute it. What the Institute adds is a naming scheme and a rule of thumb. It records that a single wrap layer of Grade C is unsuited to fragile small objects, because the bubbles are larger than the points of contact and leave a hard seam between them.
The Institute measured the diameter of a sample of bubbles across three rolls of each grade, taking ten readings per roll with a dial caliper along the widest point. Heights were read at the centre of each bubble. The sample is small and the Institute does not generalise from it, but the three diameters recurred in every roll.
Bubble wrap is classed in the Department of Thickness and Gauge, since protection here depends on how much material, or air, stands between a blow and an object. Compare the treatment of thin stock on the playing card thickness page and the wire measures on the wire gauge page. The general department note is at the Department of Thickness and Gauge.
The review panel divides on whether the Fine grade should be split in two, since some rolls sell with bubbles near 6 mm. Two members hold that these are a separate grade. The majority keep a single Grade A and note the smaller bubble as a variant, on the ground that the 6 mm roll is rare in the sample. The scheme above is the majority one.
The Institute does not publish a drop-test result, and nothing here is a guarantee that an object will survive a given fall. It publishes a naming scheme and a rule of thumb, so that two people discussing a roll of bubble wrap can mean the same thing.