Why do the British mix metric and Imperial measurements?

Question

I was in the queue in B&Q earlier. Someone quoted the width of a shed in metres, and the length in feet! This took some working out as he didn't specifically state feet or metres, so it sounded like he wanted one of ludicrous proportions.

The next man wanted 4 linear feet of 9mm window beading.

Why do we do this?

Answer 1

It seems crazy to mix units but I think the general problem reflects our failure to wholeheartedly embrace the metric system.  This is partly because of inertia in our tradespeople (and for some time in our manufacturing industry when we had one to speak of) and partly because metrication was not on the agenda among our main trading partners.  Times change and so do trading relationships so I think the balance is shifting.

I was raised on imperial measures so they are more immediately meaningful to me (though I am changing).  Some common products are standardised as a metric size (e.g. 15mm copper pipe) though many users (like me) would still conceptualise pipe runs in feet so I can understand the window beading customer you mentioned though not the person who gave mixed metric and imperial dimensions for a shed.

Answer 2

Metric is much easier to do maths in, but Imperial is based on natural feeling quantities.

Answer 3

It is a common thing in countries that changed some measurement system, eg. gallon to liter, old francs to francs, etc.

The window may have been build before metrization and the tape sold in 9mm widths.

Answer 4

What drives me to distraction is the mixing if centigrade and fahrenheit.

I m pretty much converted to metric now its much easier to use and universally accepted in Science. Don t expect our cousins across the water to change anytime soon though. Want confusion try converting feet-pounds.

Answer 5

Napoleon finally got his way when we had the metric system imposed on us . However , I still think and measure in Imperial and I am too old to change now.

Answer 6

well most manufacturers will use metric, hence the 9mm, because its more accurate. But people will find imperial useful, cos its more familiar in some cases. I for example use metric for a lot of things, because i'm quite scientific, but measuring lengths, I just compare them to either my height, 6ft, or to footlong or 6 inch subway sandwiches, its habit.

I actually imagine 4 subway footongs for something 4 foot, its crazy.

Answer 7

Only reason I can see for the shed being dimensioned in mixed units, is they may have had a tape measure that was long enough to measure the width in meters, and could only measure the length using an imperial one (I'm guessing the length was longer). You're right in thinking they should really have said what the units were!

But then again the units of [m][ft] for an area is still a VALID unit of area, it's just lack of familiarity which what makes it awkward for use. It's easy to convert once the units where stated because to convert [m][ft] to [m][m] you only need to apply the [ft] ->[m] conversion ONCE.

4[ft] of 9mm beading Doesn't sound too ridiculous to me. (At least he stated the units.)

It boils down to how you parse the sentence. While it's true that 4 ft and 9mm are both kinds of length, they clearly refer to different measurements. I'm guessing he's either a glazier, or someone who's read a book on DIY and doing a bit of work after reading up on the subject. To do the task, he's probably been told to "measure the required length, and then get that length in "9 mm beading". In his mind the "9mm beading" refers to a SINGLE thing rather than being beading with properties of 9mm, and 4ft

Also I'm fairly sure beading is dimensioned by the side lengths of a rectangle forming the CSA it's cut from.If there's only one length given, then it's cut from a square. So 9mm beading would be the same as 9mm * 9mm beading, Simply saying 9mm loses some of that information but everyone knows what they are on about, but only through CONVENTION.

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metric is only really superior if you need to change the SIZE of unit say inch to feet, and don't know the conversion factor. You still have conversion factors in metric but they're a lot easier being based on powers of 10, and because they are the same for ALL units, once learnt for one unit, they can be used for all.

imperial units do have some advantages when doing calculations by hand/mentally, where units have factors of 1,2,3,6,12 etc in common. When there's common factors a great many shortcuts can made which speed up/ease calculation. Metric is limited to having 1,2,5,10 etc in common, and so these "shortcut" methods are rairly taught today

As it happens I find it difficult to remember the factors required in imperial and will work in metric when possible. If I need an answer in imperial for all but the simplest sums, I'll convert the "inputs" to metric, get the answer, and convert back to imperial.

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Maths simply doesn't care which you do it in, as all it cares about are ensuring the relationships between numbers remain correct

Physics does care as the "numbers" mean something in the real word. (it uses arithmetic to process them.)