Shopping - Big Packs, Small Value? How to calculate the true value of the "bargain"!

Is bigger always best value?
Is bigger always best value? | Source

Buying in bulk isn't always cheaper!

Many people intuitively think that buying larger quantities in shops will give better value for money. After all, surely one large packet is cheaper to produce than two smaller ones - isn't it?

Take for example a 1kg. box of breakfast cereal and compare it with two 500g packets. A single box, you might think, would use less overall packaging (and so be better for the environment as well), take less time to fill, need less manual handling, etc. etc. and so might be the same price as the two smaller boxes, or be slightly cheaper.

Be careful - this is not always the case! "Clever" (!) marketing can be very misleading. Fortunately, armed with a small calculator, it is very easy to compare the offers in seconds. As I'm writing this in the U.K. I'll give an example using British pounds (£) as currency, and weights in kilograms, but it will work equally well with other currencies and other weights.


How to compare the offers

What you need to know is the "cost per quantity". Learn these three words now, in that exact order. Cost Per Quantity. Also learn that for the purposes of this little exercise, "Per" means "divided by".

Let's look at an example. A supermarket is selling a 1kg. box of cereal for £2.84, and a 750g box for £1.96. It isn't immediately obvious which gives best value, so you might just assume that the biggest box will work out cheaper, and so go for that.

OK, lets work out the cost per gram. On you calculator, work out the "Cost" (type in 2.84) "Per" (press the divide key) "Quantity" (press 1000, as 1kg. equals 1000 grams).

That works out to £0.00284 per gram (less than one penny).

Now let's look at the smaller box. Type in the "Cost" (1.96) "Per" (press divide) "Quantity" (just 750, as the weight is already in grams, not kilograms) and you get the answer of £0.00261 per gram. Very slightly cheaper! At less than a penny per gram, it may be not worth bothering about, but imagine this on a month's family shopping for joints of meat, bottles of milk, wine, "3 for 2" offers, "buy one get one free" offers etc. etc. You might be surprised how much you are mislead.

Ignore how many boxes and bottles you get with these offers. Just add up the total quantity you'd purchase, divide buy the total cost you'd pay, and see the true cost per gram, pint, litre or whatever.

Happy shopping!

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Comments 2 comments

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Rain Defence 4 years ago from UK

Although it is possible to do it this way, supermarkets have a cost per kilo/item/litre etc on the shelf label of all of their items now, so if you're unsure, just read the label.

It is the same method as you're talking about, but without any of the calculations as they're done for you.


Mark 1 4 years ago from UK Author

Hi, thanks for your comment. I quite agree that many do, and I always look for that myself. However, I've noticed that some supermarkets don't always include that information with their special offers tickets, so while a ticket for a single packet might show the cost per gram, the "buy two get one free" ticket often doesn't.

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