Quite a lot! In fact, my poor LCB had been so neglected I had forgot how much it can hold. I needed to use it for a night out at the Gartenschau with the kids, and I was going to carry my own collapsible chair using its backpack straps. So my go-to S25 was not going to work. I was able to carry all the important stuff in the LCB, and the extra things like a quick dry towel, snacks and water in a ssb. One of my favorite features of the LCB is that extra handle on the top back of the bag--it makes it super easy to clip to the stroller and not have to carry it all the time.
In the front zip pocket: OW, folding wayfarers, distance glasses
Center pocket (iphone not pictured): nordic SE w/wallet/phone, steel SE with baby stuff, SYSS with sock knitting, 311 cube, red rain jacket in its pouch