> We use all kinds of weird units. > Grit is based on the amount of particles that fit through an inch square. I'm aware. But I'd say its mostly used as a dime

> We use all kinds of weird units. > Grit is based on the amount of particles that fit through an inch square. I'm aware. But I'd say its mostly used as a dimensionless. When I argue "we use metric except for these few" I mean in the cases where the unit (a length, mass, pressure etc) is actually uttered or written. In some cases as you note there are labels which have non-metric definitions underneath, such as sand paper particles having a never-pronounced inch definition. The same goes for some weapon calibers where you might say a ".303 cartrige" for rifle ammunition but you'd never say a ".303 inch cartidge". A lot of people probably use these labels without knowing they are using an imperial definition. And that (I'm guessing) is also part of why it survived the metrification. > I've never seen acceleration in m/s2 outside a physics problem, otherwise it's either G or seconds to 100 km/hr. "10s to 100km/h" is as metric as m/s2 though (But again not pure SI). g being a constant obviously has no explicit unit, it's as metric as you want it to be :) I hear "5g" as 5x9.82m/s2 but an american probably hears something else.