Micrometer thimble The UK started to switch from Imperial units to Metric in 1965 - and we're still not there!

Our membership of the EU in 1973 meant that we were supposed to transfer to metric completely. Since 1995 all goods sold in Europe had have to display metric weights and dimensions but following an outcry in the UK, we were allowed to also use Imperial units. This concession was due to expire in 2009 when all Imperial units were supposed to be banished from products but the EU eventually gave up and so today we have mostly metric but still a stubborn set of Imperial units that isn't going away.

Personally, I will not buy milk in anything but pints. I can easily make a pint of custard, or fractions thereof, but I would have to think carefully about making 500ml and whether it would serve four people.

Imperial units are still used (though sometimes metric is also shown) for:

  • Railway network - miles and chains
  • Road network - yards or miles and fractions, speeds in MPH
  • Horse racing - miles and furlongs
  • Milk, beer and cider - pints
  • Printed circuit boards - 0.1" hole pitch
  • Golf courses - yards
  • Food energy - calories
  • Maritime - fathoms
  • Fuel consumption - miles per gallon
  • Gauge of firearms - e.g. 12-bore means that 12 spheres of that gauge can be made from one pound of lead
  • Newborn weights - pounds and ounces (often any weight given in kilograms is followed by blank faces)
  • Printed photographs - 6" x 4", 7" x 5", 10" x 8", etc.
Stanley tape measure

Measuring tapes in the UK still have the primary scale in feet and inches and the inches are divided into halves, quarters, eighths and sixteenths.

On a recent trip to New Zealand it was odd to see food energy content only in kJ with no Imperial equivalent. Also in NZ jam, for example, is sold in 500g jars, not the 454g jars as in the UK that are equivalent to an Imperial pound.

The only countries that still use the Imperial system are Myanmar (Burma), Liberia and USA. Myanmar generaly uses the Burmese units but government uses both Imperial and metric inconsistently. Liberia, beginning as a settlement of the American Colonization Society, uses USCS units and does use metric but has not officially adopted it.

The USA, of course, uses the Imperial names of units but they've mangled the amounts: e.g. 16 US oz to a US pint as opposed to our 20 Imperial ounces to an Imperial pint but neither the ounces nor the pints are the same. Have a look here.

USA metric road sign America began testing road signs in kilometres under President Jimmy Carter who supported efforts to go metric. Interstate 19, which connects Tucson in Arizona to Mexico, was a test route and today remains the only highway in America with distances to destinations shown only in kilometres.