Butter stick at least in America normally have tablespoon marks on the wrapper. That said, sometimes the wrapper is clearly shifted one direction or the other so that the first or last “tablespoon“ is not a full tablespoon.

Butter in the USA is sold in 1-pound boxes, each containing four quarter-pound "squares" that are marked with tablespoon and fractional-cup gauges. Simply slice off five tablespoons. (There are "Eastern" and "Western" square sizes, depending on where you live.) See: https://en.wikipedia.org/wiki/Butter#Packaging

Indeed, how would you slice cold butter by grams? Is there even a procedure?

Easy. Just slice of parts into your bowl until the scale shows the desired weight. I am a bit envious of American butter packaging, because it saves so much time, but if they ever change anything about it, you are all hosed, because nobody will know what 5 tablespoons was supposed to mean. ;-)

> how would you slice cold butter by grams?

It's more sensible than slicing off butter by spoons, where a spoon is not a square, except the slice of butter is a square!

Butter sticks in the US have marks down the side of the wrapper, like a ruler, that show you tablespoon increments. Google image search "tablespoons butter stick".

In case you are wondering how this works in practice, American butter typically comes in "sticks". Each stick weighs 1/4 pound, and is individually wrapped in foil or paper. These wrappers are typically marked in Tablespoon increments with 8 Tablespoons (1/2 cup) per stick. Measuring Tablespoons of butter just involves looking at the markings on the stick (or visually estimating the number of 8ths) and cutting off the chunk that one needs.

That does provide a method to the madness, thanks.

But... butter being measured in "cups" and "tablespoons", which are multiples/fractions of a 1/4lb block, is therefore fundamentally a unit of weight, not volume?!?

That's even more wild.

Also, that will greatly simplify the conversion process for me in the future.

Previously, when I've come across a US recipe requiring cups of butter, I've looked up the size of a US cup - which is given in fl.oz - converted that to ml, and then found a good estimate for the density of butter, and used that to convert to a weight in grams - which I can then measure easily.

If I'd known that "a cup of butter" was not really meant to be an actual "cup" measurement, and was actually shorthand (longhand?) for "0.5lb butter", that would have made conversion So. Much. Easier.

Seriously, wtf.

(I take it that other "cup" measurements are actually meant to be volume measurements, and I should measure cups of flour/sugar/etc... (and liquids, obviously) in volume-marked measuring containers?)

In the US, our butter comes in wrappers that divide each stick into 8 tablespoons, so it's actually very easy -- you can visually see where to cut.