Measurement: unit systems: hard and soft conversions

Self-tutoring about unit conversions: the tutor mentions hard and soft conversions.

The following is according to my understanding.

I mention in my post from May 3 about witnessing Canada’s conversion to the metric system in the 1970s. However, in my reading, something came up I wasn’t expecting.

Apparently, when converting from one system of measure to another, there are two “stages” of adoption. Soft conversion means simply converting the units, mathematically, from the old to new system. For instance, 13/16 inches is 20.6375mm.

Hard conversion involves manufacturing items at slightly [perhaps] different sizes so they are convenient measurements, number-wise, in the new system. For instance, a board that was 24 inches long is actually 609.6mm, or 60.96cm. However, in the case of hard conversion, that board may then be replaced, in production, with one that is 600mm, or 60cm, long. Its length has been changed slightly in order to be a convenient number of metric units.

So, hard conversion actually does change the unit sizes of products. However, one hopes not by much.

Interesting, eh?

Source:

Eric Ross, “Soft vs Hard Metric Conversions,” (2018). American Society of Professional Estimators.