What Is a Carrier Bag? | Types, Materials & Rules Explained

A carrier bag is any bag made of paper or plastic provided by a shop to carry purchased items home, and it is also known as a shopping bag or retail bag.

You grab one at checkout without a second thought — but the carrier bag sitting in your hand has layers of regulation, material science, and design behind it. Depending on what it’s made of and where you shop, that bag might be taxed, banned, or certified compostable. This guide breaks down exactly what a carrier bag is, the materials it’s built from, the sizes you’ll encounter, and the rules shops must follow.

The Official Definition of a Carrier Bag

At its simplest, a carrier bag is a paper or plastic bag handed out by retailers so customers can carry their purchases. The Cambridge Dictionary defines it as “a large paper or plastic bag given to you in a shop to carry the things you have bought.” UK tax authorities provide a more formal definition: any bag of any size or material intended for single-use transport of goods, whether used as packaging or just for carrying items. In the US, the term is less formal — most people just call them shopping bags or grocery bags — but the function is identical.

3 Common Materials Used in Carrier Bags

The type of material defines how the bag behaves, how long it lasts, and whether you can recycle it or compost it. Three materials dominate the market.

Plastic (Polyethylene)

Most plastic carrier bags are made from polyethylene — either low-density (LDPE) or high-density (HDPE). LDPE is flexible and moisture-resistant, making it a common choice for apparel packaging and soft mailers. HDPE is the crinkly, more rigid variety you find at grocery store checkout lanes. The key advantage: plastic holds up far better than paper when it gets wet. In England, plastic bags thinner than 70 microns with handles must carry a mandatory charge. Tanzania’s technical standard sets a minimum film thickness of 30 microns for general-purpose bags.

Paper

Standard paper bags are widely used for non-fragile items. They offer a more natural feel and can be recycled more easily than plastic. The trade-off: paper bags lose structural integrity in rain, making them a poor choice for wet conditions unless they are coated or laminated.

Compostable / Biodegradable

Compostable carrier bags are made from renewable resources like corn starch or sugarcane. To be certified compostable in industrial facilities, they must conform to standards such as BS EN 13432:2000 or ASTM D6400. Notably, “oxo-biodegradable” bags — which use metal salt additives to catalyze degradation — are chemically distinct from plant-based compostable bags and may not meet the same composting standards.

Carrier Bag Sizes and Dimensions

Carrier bags come in a range of sizes, but common standards exist. A “bag for life” — the thicker, returnable style — must have both width and height exceeding 404 mm, with either dimension exceeding 439 mm, measured without considering gussets or handles.

When calculating the right size bag for a product using a loose fit method, add 3 inches to both the item’s width and depth, then add half the depth to the length. A large polypropylene bag for life can also hold up to 25–30 kg of items.

How Carrier Bags Are Regulated

In England, the Single Use Carrier Bags Charges Order requires sellers to charge a minimum of 10p for every new single-use carrier bag. That charge applies only to plastic bags thinner than 70 microns with handles. Several exemptions exist: bags for unwrapped food (human or animal), loose seeds, axes and knives, prescription-only medicine, uncooked meat or fish, live aquatic creatures, and “bag for life” products that meet specific criteria — 50–70 microns thick, at least 404 mm in both dimensions, sold for 10p or more, and returnable for free replacement.

Manufacturing standards also govern quality. Bags must be free from defects like gels, streaks, pinholes, foreign matter, cuts, or tears. They must be capable of being opened readily by hand. For printed plastic bags, the ink must be Type A (single resin-based, co-solvent polyamide) or Type B according to standards, and the unprinted bag weight must not deviate by more than 1.125%.

Common Mistakes People Make

One frequent error: assuming any thick plastic bag is automatically a “bag for life.” It must meet specific thickness, size, and returnability criteria to avoid the 10p charge. Another pitfall is confusing biodegradable bags with oxo-biodegradable ones — the latter use metal salt additives and may fail industrial composting certification. Many shoppers also grab paper bags for wet groceries, only to watch them collapse; plastic is the superior choice when moisture is an issue. In England, using a bag thinner than 70 microns without paying the charge also breaks the law.

For those hauling heavy or awkward gear, a standard carrier bag simply won’t cut it. If you’re transporting a bicycle or large sports equipment, check out our tested guide to the best bike carrier bag options — built for durability, straps, and weather resistance that a thin plastic sack can’t match.

Carrier Bags vs. Other Bag Types

Carrier Bag Checklist: What to Know Before You Buy

Keep three things in mind when choosing a carrier bag for retail or personal use. First, check the material — paper works for dry items, plastic for wet conditions, and compostable for eco-conscious programs. Second, know the local charging rules: if you are a retailer in England, any plastic bag under 70 microns with handles must be charged at 10p. Third, examine the size: confirm that the bag’s width and height fit your products, using the loose-fit calculation method when needed. For reusable programs, a certified bag for life that meets the 50–70 micron and size thresholds will save you the per-bag charge.