Click on the link above and you’ll see the pullman I use.
The dimensions are 21 x 12 x 11.5cm H and they recommend it for a 1lb loaf. However that seems to be a mistake and it fits a 2lb loaf perfectly.
Let me just convert that into inches : 8.27 inches length x 4.72 inches width x 4.52 inches height
I think it’d normally be too small for a 2lb loaf but it’s quite deep so it fits snuggly and rises well.
So 9 inches length (slightly bigger) - but a normal pullman being a smaller width and height then mine - seems perfect for a 2lb loaf.
If yours is a 13" pullman you’re looking at a slightly larger loaf of 1130g instead of a 900g loaf. I reckon you can fit an extra 200g of dough in the 13".
It also depends on what type of dough, hydration, flour and how much you expect it to rise. But as a rule of thumb 500g flour for a 2lb loaf and 640g ish flour for your pan.