Have you ever torn open a packet of chips only to discover the bag is half-empty? Or opened a box of snack bars to find they're much smaller than you expected? And that expensive jar of moisturiser – why is it only half the size of the box it comes in?

You'll find plenty of products brimming with lots of empty space. Manufacturers might blame packaging processes or labelling information, but you're probably just wondering what on earth happened to the rest of your product.

The case of the disappearing products

A classic packaging trick is to shrink products and keep the packaging the same. In some cases, products are redesigned to mask the smaller size. Foods such as cereal in boxes might go down in weight, but the box stays the same or is altered in height and width so it's not immediately noticeable.

Canny CHOICE readers have spotted examples of shrinking products over the years:

  • The size of chocolate bars is reduced, but the number of pieces stays the same.
  • Toilet rolls still look the same on the outside, but have fewer sheets because manufacturers have increased the diameter of the cardboard tube in the middle.
  • Breakfast cereals shrink in packet size but not in box size.
  • Man-size large tissues shrink in size, but not in name despite being significantly smaller.
  • Packets of chips shrink in contents, along with price, but the packet stays the same size so it looks like a saving.
  • Some soap looks the same until you take off the wrapper and discover the new bars have been cunningly reshaped to be more concave so you actually get less soap per bar.

Regulating product packaging

Misleading packaging is difficult to prove, as products are sold by weight or volume, which is usually stated. If it says "350g" or "4 bars" on the packet, that's what must be inside, and that is what's regularly checked by fair trading agency officers to ensure consumers are getting what they pay for.

Whether there's room for a fifth bar, or another 50g of product, isn't specifically addressed in the relevant regulations. In Australia, food packaging is administered under state and territory trade weights and measurements acts.

While the federal Trade Practices Act and the various states' fair trading acts include provisions against false and misleading conduct, excessive packaging in itself is not considered misleading. This means a bigger box isn't necessarily breaking the law as long as it's got the right weight or number of servings.

How much empty space is allowed?

Snack foods of a fragile nature, such as chips or crackers, are generally loosely packaged and padded by air to protect them from being crushed and ending up as slack fill crumbs. A reasonable amount of empty space, or "air cushioning", is permitted by law – 25% for cereals, for example, and 40% for delicate snack foods.

According to Ian Greenshields from Goodman Fielder, manufacturer of the Veri Deli brand, a bag of Rosemary & Sea Salt Cracker Snacks "has 22% free air space, which is well within the allowable limit". Yet when you open the bag – and after the contents have settled – the air space looks decidedly bigger.

Even the time when potatoes are harvested can have some bearing on the air content in packaging, as is the case with Kettle Chilli Slow Cooked Chips. "They vary in density throughout the growing season, which means at certain months of the year the chips take up more space in the pack for the same weight than at other times," says Matt Jenkins from Snack Brands Australia, manufacturer of Kettle Chips. "Our packaging has to accommodate this variation in size and density."

Room to move

"We always aim to ensure the product volume is at least 70%, typical of industry targets," says Bryce Howard, spokesperson for Tasti Products (which manufactures WeightWatchers Macadamia & Cranberry Cereal Nut Bars under licence). But without their plastic wrappers, and neatly packed next to each other, these bars (pictured right) leave a lot of empty space in the cardboard box in which they come.

Howard told CHOICE the company uses the same size boxes for different products to make the production process more efficient, allow for machine tolerances (because the ingredients vary in size and density by season and source location) and accommodate the machines' extreme high operation speeds.

Which bag of sugar is bigger?

These two packets each contain 1kg of raw sugar, but one uses more packaging than the other and takes up markedly more shelf space − and is, therefore, more likely to attract your attention in the supermarket than the smaller packet. One theory is that it's designed to make you think you're getting more than from the competitor's brand.

The manufacturer of the larger bag offers other reasons for its choice of packaging. Sugar Australia, which makes CSR products, says while the bags used for its white and raw sugar are of a similar size, the packaging material and design are different. The white sugar bags are made of paper and the head space is folded and glued down, whereas the bag for raw sugar is plastic and not folded over. The company says this is because raw sugar is hygroscopic, meaning it takes up and retains moisture readily, so plastic bags provide better protection.

Big on labels, small on size

Some manufacturers use the argument that certain products need large labels, and thus larger containers, to display important information. CHOICE found the example of vitamins and supplements in containers that are only half full.

The manufacturers argue that the information that needs to be included on the label won't fit onto a smaller bottle in the correct font and style.

In other cases, food manufacturers say that the limitations of packaging machines means that certain products are packed with more air because the packaging can't be reduced. This equipment is a sizable investment so manufactures are probably reluctant to replace equipment unless they have to in order to make savings or comply with the law.

Don't fall for the shrink tricks

  • Check the weight of the package or the number of items it contains. A larger package doesn't always mean more contents.
  • Compare prices for a comparable unit by volume or weight. Unit pricing allows you to compare prices easily between grocery products packaged in different sizes. It's now mandatory for larger store-based, online and grocery retailers.
  • Don't buy a product if you believe it's deceptively packaged. Let the company know why you're rejecting it and, if you're concerned you've been misled, report the matter to the ACCC or your state or territory's Office of Fair Trading.