Pack sizes to liters?

I have pencil and paper in hand and I am going to sketch out my pack I am wanting to build. What is the standard liter size of a g4 style pack ? I am going to make my pack out of old tent material I have and I am hoping it will be enough. I was going to design it around the g4 shape but now that I keep looking at pics of packs on line, the simple shape of a stanadard z pack zero looks a bit easier for me to make with my lack of sewing skills. Of course I know that this first pack I build will there will be a larger learning curve and I will have more to learn as I go on. To me, some of the z packs just look like a standard large stuff sack with straps and a closure and a wider bottom and I will make side panels so I can make holders for water bottles> the plans on the g4 page I found on line.

Why not contact Gossamer Gear directly with your question? Asking the size seems a reasonable question to me. Talking to them directly might give you a bit of insight as to how the pack is designed.

G4 is listed as 54L pack. I think you want something in the range of 50-60 liters, or in cubic inches - 2000-3000 (probably somewhere in the middle).

Little low on the c.i. . 61.2 c.i. per liter. Not that it matters much, but over 3,000 c.i. for a starting point. 54l is > 3300 c.i. I've used roughly this size pack for about the past 10 years, and it suffices for lightweight, multi-day and even winter use.

G4 is sufficient for my winter use in Wisconsin for up to 5 days. And if you have to go for longer, you just need to resupply more often which isn't difficult in Wisconsin.