Metric and English Conversion

[George Neill]

Inching Forewards casts some light on the history of both systems of measurement. Also, check out the links in Pat Naughtin's comment at the foot of the page.

[Darius Ferlas]

I think you're making my point for me. While cubic decimeter may be an official SI unit, people use liter. They use it because it is a convenient size. Cubic meters is a convenient unit if you're buying some things -- for instance concrete -- but not so convenient if you're buying others -- for instance Coke. Cubic decimeters, while an ideologically pure unit, is too much bother to write out.

Some do, some don't. I'm actually one of those "people". I didn't know what an inch was until the age of 26.

A lot depends on the context, material, country and tradition, even though Europeans will easily switch from one metric unit, or its representation, to another. My point was not the actual usage of the decimeter and I agree, it is not used as frequently in the context of volume as liter, but the usage is certainly not unknown (example below).

Decimeter is not as hard to write out either. How hard can it be to write dm3 for volume (where 3 is a superscript), or simply dm for length. A liter is not any more convenient than dm since both are exactly the same when it comes to volume.

Some practical examples of usage: if you or I buy a bottle of coke it will be either 335 ml, 1L or 2L. In some EU countries you can buy a quart/quarter of some fluid, i.e. 0.25 of a liter (a capacity of a standard glass/mug). That's for personal consumption. A major bar (I mean really major) may buy a few thousands of liters, or a few hectoliters (hl). When I had a Summer job in a winery and distillery all containers were marked in hectoliters. But when you buy a shot of vodka it's often in grams rather than milliliters (50 grams please) even if volume measuring cup is used instead of scales. The two are not 100% equivalent but close enough and after a few those fifties (1.7 fl.oz. straight as ice and such are for sissies) few could tell the difference anyway.

Concrete, even in the fluid form will be sold by cubic meters (m3) just like lumber. But when you buy a single board you will buy a single board of dimensions specified but your vendor bought it in cubic meters as a part of a larger shipment. However weird it may sound, from the point of view of your vendor he will sell you (as an example) 0.0039 m3 of wood, not 3.9 liters, or 3.9 decimeters or whatever the unit the buyer might consider more convenient.

In dry form, concrete and sand will be sold by kilograms (if bought as individual bags) or by tonnes (even if you order a truckload of individual bags). The water you add to it will be in liters or hectoliters and that will depend on the size of your job. If you pour concrete into forms to create cubes of 10x10x10cm you'll get 1 dm3 cubes (1 cubic decimeter), not 1 liter cubes, even though you use 1 liter of wet concrete.