US and metric cooking units

[charmanjoe]

Some units are in metric while others are in US units. For example:
math.unit(1,"cup").toNumber("tablespoon")
15.772546666666665
From here, a US legal cup is 240 mL, while a US customary cup is 236.5882365 mL.
From here, a metric tablespoon is 15 mL, while a US tablespoon is approximately 14.8 mL.
From my example, it seems like it uses a US customary cup and a metric tablespoon.
Please include the option for US units.

[josdejong]

Hm yes you're right, we should change the value of tablespoon to ~14.8 mL to make it consistent with cup. And probably create new units for the other variants of the units.

[charmanjoe]

Here is a list of the United States Customary Units.

[josdejong]

Who's interested in fixing the these units?

It will be a breaking change so we'll have to schedule it for v6

[codingedgar]

I haven't found anything that solves the US system, Imperial, Metric differences of cup, Tbs etc well, same issue happens in measuring-cup. The need of

1. Transform between systems (US, Imperial, Metric, etc)
2. Transform between units (cup of sugar -> g of sugar)

Are very common use cases for cooking, (the 2nd point is a total different issue, but would be amazing to have something to do it)

[ericman314]

I've been working (very slowly) on migrating all the units functions from math.js into their own library. Would you mind raising this issue over at https://github.com/ericman314/UnitMath/issues ? That way I will not forget about it. I imagine that this might be something we could address with a configuration option to choose between the various types of cups, etc, or have units with suffixes such as cupImperial, with an alias of cup, depending on the configuration option.

[gwhitney]

Since this is recorded over at UnitMath, closing it here (as it is more likely to be resolved over there than here, I'd say).