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Most of the world is metric and has been for a long time. The USA is still imperial which can lead to disaster if conversion is not done thoroughly and accurately. There are many hideously expensive examples of imperial and metric conversion mistakes from construction in sports to space.

With a lot of builders in the UK being Polish or European, of course they are all metric. Older builders in the UK will think in feet and inches, younger builders can usually rapidly convert measurements in their heads.

And IKEA, B&Q and so on all work metric so people are now used to metric.

Metrification of the UK building industry dates back to about 1970-1975. However builders in the UK still talk of 2 by 4s and so on which is all inches. Most people in the UK still think in imperial measurements. Except Architects of course.

In practice, wood is still sold in 2 x 2s, 2 x 4s, 2 x 6s... and 6 feet and 8 feet lengths. The displayed measurements are all metric as it is illegal to display imperial figures, the guys just cut it to imperial lengths. The Empire strikes back...

There is a funny standard where small distances are spoken of in millimetres and larger ones in feet and inches. Centimetres are popular in ex-Imperial countries as they are like little inches, 30 (actually 30.48) to a foot. Millimetres are universal, centimentres are annoying as you have to use a decimal point for small distances. So an Architect will say a room is 4557 mm across. What? Is that for ants to figure out?

Some use of imperial units is still present in old British colonial countries such as South Africa, Zimbabwe, Malaysia, Singapore, Hong Kong, Australia, New Zealand, Canada, USA, and Ireland.

Bricks are now made in metric but older houses are all imperial so there is a huge trade in old bricks. This is due to aesthetics as well as planning regulations especially in conservation zones.

Remodeling and refurbishment

Older buildings may be all laid out in imperial units so you might wonder why nothing fits properly. Also be aware that area measurement is very resistant to change, with some country folk still going on about perch, rood and acres. Or for length, rods and chains. Tally ho!


New metric bicks are smaller than the old imperial ones, so if doing a rough job you can increase the mortar size. This will look horrible though, so it depends if the wall is being clad or rendered.

Unlike the length, in the UK the depth of a standard imperial brick was less at about 2 inches or 51 millimetres. A modern metric brick is about 2.5 inches or 64 mm.

American US bricks are 8 inches x 4 inches x 2.25 inches (203 x 102 x 57 mm).

South African bricks are 8.75 x 4 x 3 inches (222 x 106 x 73 mm).

Australian bricks are 9 x 4.33 x 3 inches (230 x 110 x 76mm).


Softwood went metric in 1970. It is sold from standard lengths starting at 1.8 metres (just under 6 feet). (Can be used to measure 6 feet under if you have any cemetery jobs).

Lengths increase in 300 mm steps up to 6.3 metres (about 20 feet 8 inches).

Generally the metric equivalents are slightly shorter that the imperial lengths. (Cue moaning from Little Englanders circa 1970, BBC TV retro documentary etc.)


Hardwood (as more expensive and less used ror general jobs) starts from the standard length of 1.8 metres and goes up in 100 mm steps ie 1.9m 2.0m, 2.1m etc.


Paint went metric in 1971 and comes in litres and millilitres.

A 250 ml tin is just under half a pint.

No one thinks of paint in pints now, but they still think in terms of pints of milk.


25mm is a 1 inch brush (all slightly smaller than imperial sizes).

50mm is a 2 inch brush (etc)



For many other types of conversion see Unit Conversion Org >