METRICATION:  100% complete
Metric Non-metric
Floor coverings manufactured in metric widths
Unit pricing : per square metre

Measurement units

Quantity Old unit Metric unit Symbol
Area square yard square metre m2
Carpet length and width foot, inch metre m  

Metric unit pricing – 2019


Following the successful decimalisation of currency in 1971, metrication of carpet sales finally began in 1975.

In February 1975, carpet retailers agreed to switch to metric unit pricing for carpets and floor coverings. The voluntary move was backed by a public information campaign run by the Metrication Board.

Aids included a handbag/pocket aid for customers comparing metric weights and measures with imperial, and various wall charts for retailers showing, for a range of prices per square metre, how much customers would be paying for a square yard.

Customer information also appeared in full page advertisement slots in popular magazines.

Carpet sales metrication – magazine advertisements – 1975

Initially, the change to sales by the square metre went well, but in 1977 one of the major High Street retailers found commercial advantage in reverting to sales by the square yard. It seems consumers were not easily convinced that retailers pricing a carpet at £10 per square yard in one shop, but £12 per square metre in another shop, were actually charging virtually the same price. Retailers that had hitherto stuck with metric unit pricing were left with no alternative but to follow suit and revert to sales by the square yard.

Consumers were aware that one metre is “just a bit longer than a yard”, but it was not widely understood that a square metre is almost 20% more than a square yard.

The metrication of carpet sales had failed because a cut-off date to end imperial unit pricing had not been set. The need for legislation had been neglected.

The experience of carpet sales in the 1970s was in stark contrast to the metrication of pre-packed foods that was happening at the same time. Following prior agreement with affected industries, cut-off dates, for the withdrawal of imperial prescribed quantities for various pre-packed foods, were backed up by legislation. The result was a smooth event free transition.

In 2000, legislation finally came into force that switched unit pricing for all goods to metric. However, imperial unit pricing was allowed to continue in the form of supplementary indications alongside metric pricing. Supplementary indications were permitted as long as they were not more prominent, or in a text size that was larger, than the metric unit price.

Even after 2000, at least one major retailer tried to claim a commercial advantage by pricing per square yard in a market that was predominantly pricing exclusively per square metre. Price labels were divised that tested the legislation to the limit. Imperial supplementary indications were not larger than the metric unit price, but it could be argued that the use of colours and price points made the imperial price more prominent.

Prominent imperial unit pricing – 2006 

Unit prices in square yards might be attractive to traders, keen to make their wares look cheaper than they really are, but for consumers, square yards are particularly unhelpful. Carpets generally come in widths of 2, 3 or 4 metres, and any customers who may have measured up for a carpet using imperial units, would have done so in feet and inches – imperial tape measures don’t have indications in yards.

By 2008, the use of supplementary indications had largely disappeared. In 2020, floor coverings for sale in all major carpet retailers were priced exclusively in metric units.

Why dual unit pricing is bad for consumers

“Let there be one measure for wine throughout our kingdom, and one measure for ale, and one measure for corn, namely “the London quarter”; and one width for cloths whether dyed, russet or halberget, namely two ells within the selvedges. Let it be the same with weights as with measures.”

Magna Carta – 1215

The use of a single standard measurement system for trade has been a cornerstone of consumer protection for 800 years.

With unit pricing in single standard units, consumers can compare prices in different stores with ease. However, even when all traders use the same standard metric unit pricing, the ability to compare prices can still be adversely affected if some traders opt for dual units, by showing supplementary imperial unit prices.

For instance, if a consumer sees a carpet that they like in one store, priced in dual units at £7.16/m2 (£5.99/yd2), and makes a mental note of the supplementary unit price in square yards, when they later see a similar carpet in another store that is not using supplementary unit pricing, they will be unable to make an accurate price comparison without resorting to arithmetic.

Without knowing the necessary conversion factors, and carrying out the calculation, consumers can be prone to making poor judgements when comparing prices in different units, especially when under the misapprehension that a square metre is only slightly larger than a square yard.

A unit price of £5.99/yd2 in one store can deceptively appear cheaper than a price of £6.99/m2 in another. Whereas in fact the £6.99/m2 price would be the best value.

Ending the authorisation of supplementary unit pricing will improve consumer protection.

The pre-decimal era

“The past is a foreign country: they do things differently there.”

The Go-Between, L.P. Hartley – 1953

Prior to 1971, the sheer variety of pre-decimal units, both monetary and measurement, gave huge scope for the obfuscation of carpet prices.

In contrast, the simplicity of decimal money and metric measurements are a cornerstone of modern consumer protection, providing price transparency, and ease of calculation for customers.

Carpet sales – magazine advertisement – 1959

This advertisement from 1959, serves as an example of how needlessly complex everyday calculations were before decimalisation and metrication.

The advertisement contains the following information:

Unit price: 24/6 per square yard
Largest width available: 144″
Cost of a 9 ft x 12 ft carpet: 14 GNS


  • 3 monetary units – guineas, shillings and (old) pence,
  • 3 length units – inches, feet and yards – with widths in inches or feet, lengths in feet, and areas in square yards.

Notably, pounds don’t figure anywhere in the advert at all. Customers are left to work out the cost in pounds themselves.

The numerous conversion factors required to convert between the multiple units used for each quantity were essential knowledge for consumers in the pre-decimal era.

For example, to verify the statement “TYPICAL CARPET 9 ft. × 12 ft. – 14 GNS”, a consumer would have needed to know the following:

  • “GNS” means “guineas”.
  • A guinea was an unofficial currency unit with a value equal to £1 and 1 shilling, or 21 shillings.
  • £1 = 20 shillings (20/-).
  • 1 shilling = 12 (old) pence (12d).
  • 1 yard = 3 feet.
  • 1 foot = 12 inches (12″).

Before any calculation involving unit pricing and carpet area could be done, it would have been necessary to convert all quantities expressed in multiple units into quantities expressed in single units. In pre-decimal currency times consumers would not have had the benefit of pocket calculators:

Using and pre-decimal money and imperial measurements
stated price = 14 GNS
= 14 × 21 × 12d
= 3528d
unit price = 24/6 per square yard
= (24 × 12d) + 6d per square yard
= 294d per square yard
area = 9 ft × 12 ft
= (9 ÷ 3) yd × (12 ÷ 3) yd
= 3 yd × 4 yd
= 12 square yards
calculated price = 12 square yards × 294d per square yard
= 3528d
= (3528 ÷ 12) shillings
= 294/-
= £(294 ÷ 20)
= £14.7
= £14 14s 0d
* The guinea, which consumers knew was approximately equal to £1, was used to make expensive items appear cheaper than showing their price in pounds.

With decimal currency and metric measurements, using similar sizes, the equivalent calculation is straight forward and requires no pre-learned conversion factors:

Using decimal money and metric measurements
stated price = £14.40
unit price = £1.20 per m2
area = 3 m x 4 m
= 12 m2
calculated price = 12 m2 x £1.20 per m2
= £14.40

More than 50 years after the switch to decimal currency, it is difficult to comprehend why such byzantine methods of measuring and pricing carpet were allowed to continue for so long.

Many years after road signs have finally gone metric, future generations might be similarly bewildered by today’s use of inches, feet, yards, llath and miles to indicate distances and restrictions on our roads.


Imperial measuring tapes don’t show yards.