What the Numbers on Plastic Actually Mean

The first time I held up a yogurt pot and squinted at the underside, the little triangle with a 5 in the middle, I assumed it meant the pot could be recycled. That’s what most people think. It’s also why a lot of plastic ends up in the wrong bin and, eventually, in landfill anyway. The triangle is not a recycling badge. It’s a code that tells you which kind of plastic you’re holding. Whether your council actually accepts that kind is a completely separate question.

The numbers run from 1 to 7 and were introduced in the late 1980s by the plastics industry to help sorting facilities tell one resin from another. They were never designed for shoppers. The fact that we squint at them in the kitchen, trying to decide between blue bin and black, is a kind of accident of history. the EPA’s recycling FAQ Once you understand what the numbers actually represent, the decisions get easier, even if a few of them stay annoying.

The seven codes, one by one

Each code corresponds to a different kind of plastic with different chemical behaviour, different markets, and a different chance of being recycled. Knowing the family helps you predict whether something will be collected at the kerb or whether you need to take it elsewhere.

1, PET (or PETE)

Clear water bottles, fizzy drink bottles, salad boxes from the supermarket. PET is the most widely recycled plastic in the UK and most of Europe. Almost every council picks it up. Empty it, leave the lid on (modern sorting can handle lids attached, and loose ones are too small to sort), and pop it in. Recycle Now’s how-to guide (UK)

2, HDPE

Milk jugs, shampoo bottles, the white-ish opaque containers detergent comes in. HDPE is another reliable one, kerbside collection in most areas, decent end markets, often turned into pipes, garden furniture, or new bottles. Rinse, squash, replace the lid loosely.

3, PVC

Pipes, some old cling film, blister packs for tablets, certain shower curtains. PVC is the troublemaker. Almost no kerbside scheme accepts it. It releases chlorine when burned and contaminates other plastics if it ends up in the wrong bale. If you see a 3, assume general waste unless you know of a specialist take-back.

4, LDPE

Bread bags, frozen veg bags, the film that wraps a six-pack of bottled water. Soft, stretchy, lightweight. Most councils still won’t take LDPE at the kerb because film clogs sorting machinery. Supermarket carrier-bag bins, however, increasingly do, and the network is growing.

3 sub-note on contamination

You may have read that one rogue PVC item can ruin a whole batch of PET. That’s a slight exaggeration, but the principle is real, PVC has a low melting point compared with PET, so even small amounts cause defects in the recycled product. This is one reason facilities are picky.

5, PP

Yogurt pots, margarine tubs, takeaway containers, microwave-safe tubs, bottle caps. PP used to be a kerbside maybe. Acceptance has improved a lot in the last five years, and most UK councils now take it. Check your local guide if you’re unsure.

6, PS

Polystyrene. The clamshell from a fish-and-chip takeaway, foam packing peanuts, those rigid yogurt drinks cups in airline meals. Almost universally not recycled at the kerb. The lightweight foam form is particularly tricky, it’s 95 percent air and crumbles into a million pieces.

7, Other

This is the bin-end of the system. Anything that doesn’t fit 1 through 6. Could be a bioplastic. Could be a mixed-resin laminate. Could be polycarbonate. Default assumption: general waste, unless your council says otherwise.

Why “recyclable” is local

A pot stamped with a 5 might be recyclable in Manchester, ignored in rural Wales, and burned for energy in Sweden. The number tells you the material; your local authority tells you the policy. The two only intersect when there’s both a sorting facility nearby and a buyer for the finished bale. When the market for, say, PP drops, councils sometimes quietly stop collecting it. The packaging doesn’t change. The economics do.

That’s why two neighbouring boroughs can have completely different rules. It frustrates everyone, and there are slow efforts to standardise things. Until then, your council’s website is the most reliable source, not the triangle.

The dance of the lids and labels

Bottle lids are often a different plastic from the bottle. PET bottles usually have PP or HDPE caps. Modern facilities expect this and can separate them. Leaving the cap on is now generally recommended, it stops the cap getting lost in machinery and means more material ends up sorted.

Labels are less consistent. Some are paper, some are plastic film, some are shrink-sleeve PVC. You don’t need to peel them off. The washing process at the facility handles labels just fine.

Reader question

Anita in Cardiff writes: “My oat milk carton has a triangle with a 7 in it. Should I bother?” The honest answer is: probably not at the kerb, but check whether the brand offers a return scheme. Many plant-milk cartons are technically polymer-coated paperboard and need a separate stream. Your local Tetra Pak collection point, usually at a supermarket car park, is the right home.

The codes you’ll meet most often

Run through your kitchen recycling for a week and you’ll see a strong pattern. Plastic bottles for drinks are almost always 1. Milk jugs, shampoo, and laundry detergent are nearly always 2. Yogurt pots, margarine tubs, and bottle caps are usually 5. The remaining codes show up occasionally, often on the items that cause the most confusion, a takeaway tray that’s PS, a blister pack that’s PVC, an oat milk carton that’s 7.

If you can confidently identify 1, 2, and 5 on sight, you’ve covered the majority of household plastic packaging. The rare codes don’t need memorising. They just need a quick check before binning.

The chasing arrows and what they actually look like

The triangle around the number is technically called a “resin identification code.” It was designed to look like the chasing arrows recycling symbol, which has caused most of the confusion. They look almost identical at a glance, the difference is the solid lines versus the arrow style, but they mean different things. The resin code identifies material. The chasing arrows symbol indicates recyclability.

Modern packaging is moving toward clearer labelling, with text underneath the symbol stating “widely recycled” or “not yet recycled.” This trend is helpful but not yet universal. Until it is, the resin code remains the most reliable physical indicator of what you’re holding.

The triangle isn’t the enemy. It’s just been doing a job it was never really designed for. Once you stop expecting it to give you a yes-or-no answer, it becomes a useful clue rather than a source of guilt. The rest is the slightly boring work of knowing what your council collects.

Readers who liked this often read The Curbside Recycling Mistakes Almost Everyone Makes, How to Rinse Recyclables Without Wasting Water, Recycling Aluminium vs. Steel: A Simple Guide, and A Quiet Kitchen Reset: One Drawer, One Shelf, One Habit next.