What's your pony setup?

[Manatee Diver]

So easy using SI units. Staggeringly difficult using traditional non-integrated units.

I get really konfuzed with this nominal working volume but not knowing the pressure.

E.g. how much gas is in this tank with this pressure.
SI units: wet volume (litres) x pressure (bar/ata) = litres of gas at the surface

We just use tank factors. For an AL80 it is 2.5cuft per 100psi. An AL40 is 1.3. I know the factor factors of all the tanks I commonly dive off the top of my head, and have a chart in one of my notebooks for those that I don't commonly dive. Though more likely I would just pull out my phone can calculate the tank factor.