Which? exposes poor grasp of unit pricing

The Which? consumer group published its most recent investigation about unit pricing on 23 August 2022, asking “Can you spot the cheapest supermarket prices?”. If you cannot do this, you could be missing out on huge savings. The ability to use unit pricing to get the best deals is a critical skill in the cost-of-living crisis.

Which? has designed a quiz to test the general public’s understanding of unit pricing and people’s ability to identify the product with the lowest unit price. You can find the quiz questions here followed by the Which? findings and quiz answers. The quiz results show that a substantial proportion of the population is unable to identify the best deal.

Which? Quiz Questions

Test your understanding of unit pricing by taking the Which? “Can you spot the cheapest fizzy drinks?” quiz here. The answers are given at the bottom with explanations.

Which? asks you to pick the cheapest option per 100 ml every time, to assume that all offers (e.g. Any 2 for £3) are applicable to you if you want to use them and not to use a calculator.

Question 1

Fanta cans 8 x 330 ml: £3.25 (12.p/100 ml)
Fanta 2 litre bottle: £1.70 (8.5p/100 ml) – Any 2 for £3
Fanta cans 24 x 330 ml: £8 (10.1p/100 ml) – Any 3 for £20

What is the cheapest option per 100 ml?

a) Fanta Orange Zero cans (8 x 330 ml)
b) Fanta Orange Zero (2 litres)
c) Fanta Orange Zero cans (24 x 330 ml)
d) Fanta Orange Zero (2 litres) using offer ‘Any 2 for £3’
e) Fanta Orange Zero (24 x 330 ml) using offer ‘Any 3 for £20’

Question 2

Diet Pepsi 2 litre bottle: £1.75 (8.8p / 100 ml) – Buy 2 for £3
Diet Pepsi cans 12 x 330 ml: £4.75 (12p / 100 ml) – Buy 2 packs for £8.75
Diet Pepsi 1.25 litre bottle: £1 (8p / 100 ml) – Offer price £1

What is the cheapest option per 100 ml?

a) Diet Pepsi (2 litres)
b) Diet Pepsi cans (12 x 330 ml)
c) Diet Pepsi (1.25 litres)
d) Diet Pepsi (2 litres) using offer ‘Buy 2 for £3’
e) Diet Pepsi cans (12 x 330 ml) using offer ‘Buy 2 Diet Pepsi 12-packs for £8.75’

Question 3

Diet Coke cans 24 x 330 ml: £7.99 (10p/100 ml) – With Clubcard £7
Diet Coke 2 litre bottle: £1.77 (9p/ 100 ml) – Any 2 for £3
Diet Coke cans 12 x 150 ml: £4.90 (27p / 100 ml) – With Clubcard £4

What is the cheapest option per 100 ml?

a) Diet Coke cans (24 x 330 ml)
b) Diet Coke (2 litres)
c) Diet Coke (12 x 150 ml cans)
d) Diet Coke (2 litres) using offer ‘Any 2 for £3’

Which? Findings

Which? found that 72% of people cannot identify the cheapest fizzy drinks in a range of real-life examples from supermarkets. Which? revealed you could be paying up to 346% more by choosing a different size of an identical product.

On supermarket shelves, you will see unit price labels showing you the cost of a product per 100 grams or per 100 millilitres so you can instantly see which product is cheapest. However, it is disappointing that supermarkets fail to give the unit price for special offers.

Which? found different units used for the same types of items; per kilogram in some cases, per piece or each in others. The latter can mean per item or per pack. This is a compelling reason to use a single, simple rational system of measurement, one based on powers of ten (i.e. the metric system).

Unit pricing at supermarkets is a legal requirement under the Price Marking Order 2004. Unit pricing fails in some cases because of the legal loopholes in the legislation. The Which? investigation found unit pricing was often unclear, inconsistent or missing.

Which? compared the average prices of 10 popular food and drink product types from 1 March to 31 May in Asda, Morrisons, Sainsbury’s and Tesco supermarkets. They found that unit pricing varied by 346% for Coca-Cola, 231% for crisps and 133% for supermarket brands of semi-skimmed milk. Obviously, purchasing decisions need to be based on individual circumstances and the product with the lowest unit price might not be suitable for everyone. But consumers must still be able to compare unit prices and make informed purchasing decisions.

Conclusion

The metric system makes it easy to convert between grams and kilograms, millilitres and litres because the whole system is based on powers of 10 and conversions only involve moving the decimal point. Converting whole numbers of kilograms and litres to grams and millilitres respectively involves adding three zeros to them. The simple calculations shown in the Quiz Answers section below show how easy it is to work with the metric system.

Imagine how much harder it would be to calculate if weights were only shown in pounds and ounces and volumes were only shown in pints and fluid ounces on product labels. Extra conversion steps would be required to convert the figures into a single imperial unit then convert that unit into grams or millilitres. Most people would need a calculator to do these complex conversions. I suspect that far fewer would be able to work out the correct answers to the quiz questions if quantities were given in imperial units.

This is another reason why the Government’s proposals to drop the requirement to use metric units is a bad idea. It will make it a lot harder for consumers to identify the best deals and save money and is especially bad in the cost-of-living crisis.

You can find the full Which? report and quiz at the following link:
https://www.which.co.uk/news/article/can-you-spot-the-cheapest-supermarket-prices-asvVe1C5iZMO

Which? Quiz Answers

Answer to Question 1

The unit prices without the special offers appear in Question 1. The unit prices for the special offers are calculated as follows:

d) Fanta Orange Zero (2 litres) using offer ‘Any 2 for £3’:
2 bottles contain 4 litres = 4000 ml. To get the price per 100 ml, you need to divide by (4000 / 100) or 40. £3 / 40 = 7.5p / 100 ml.

e) Fanta Orange Zero (24 x 330 ml) using offer ‘Any 3 for £20’:
Three 24-packs contain 24 litres = 24 000 ml. To get the price per 100 ml, you need to divide by (24 000 / 100) or 240. £20 / 240 = 8.3p / 100 ml.

Therefore (d) is correct. The correct answer was given by 52%. Among the 48% who got it wrong, 3% said (a), 24% said (b), 4% said (c) and 17% said (e).

Answer to Question 2

The unit prices without the special offers appear in Question 2. The unit prices for the special offers are calculated as follows:

d) Diet Pepsi (2 litres) using offer ‘Buy 2 for £3’:
2 bottles contain 4 litres = 4000 ml. To get the price per 100 ml, you need to divide by (4000 / 100) or 40. £3 / 40 = 7.5p / 100 ml.

e) Diet Pepsi cans (12 x 330 ml) using offer ‘Buy 2 Diet Pepsi 12-packs for £8.75’:
2 packs of 12 = 24. 24 x 330 ml = 8 litres = 8000 ml. To get the price per 100 ml, you need to divide by (8000 / 100) or 80. £8.75 / 80 = 11p / 100 ml.

Therefore (d) is correct. The correct answer was given by 46%. Among the 54% who got it wrong, 16% said (a), 2% said (b), 31% said (c) and 5% said (e).

Answer to Question 3

The unit prices without the special offers appear in Question 3. The unit prices for the special offers are calculated as follows:

d) Diet Coke (2 litres) using offer ‘Any 2 for £3’:
2 bottles contain 4 litres = 4000 ml. To get the price per 100 ml, you need to divide by (4000 / 100) or 40. £3 / 40 = 7.5p / 100 ml.

Therefore (d) is correct. The correct answer was given by 73%. Among the 27% who got it wrong, 13% said (a), 11% said (b) and 3% said (c).