Again this is a 'I'm personally used to this, so it must make sense to everyone' category of claim. Here in AU we use metric widely. There are some older gene

Again this is a 'I'm personally used to this, so it must make sense to everyone' category of claim. Here in AU we use metric widely. There are some older generation types that drop to imperial measurements for some things, particularly when talking about human height. A foot is about 30cm (or 300mm) - so if you're talking about working in 1/12, 1/6, 1/3, 1/4, or 1/2 of something around that size, it's not something that blocks us for very long: the calculating of fractions of 30 (or 300) units. Typically I work with metres (and subsets of) - 1000mm - which your 1/4 and 1/2 are, obviously, easy to apply and still get this enviable 'round number' that you speak of. 1/3 of a metre is 333mm (or close enough to) and it's rare that my pencil is sharp enough (or my care high enough) to denote a third of a millimetre. Similarly 1/6th (I don't recall ever needing to divide a length of anything into 1/6ths - perhaps I'm atypical). I think the most compelling evidence against any claim that 'it's easier to work in base 12' (or similar) is that our machines, our houses, our infrastructure ... don't all fail to fit together, or fall apart, because their components were measured in metric. When I say 'our' I mean the 95% of the world's population that isn't the USA.