I think a better gauge is the number of features that you can keep in your head, rather than the number of lines of code. (LOC doesn't always directly correlate

I think a better gauge is the number of features that you can keep in your head, rather than the number of lines of code. (LOC doesn't always directly correlate with complexity, anyway.) I'd say I can usually hold about 50% of the features of the projects I usually work on in my day job without having to do a "context switch". Usually, it's oriented around clear lines in the code -- for example, the latest project I worked on had a program written for a handheld computer with the .NET compact framework, a website written with MonoRail and ExtJS, and a large data migration system. If I was working on the website, I could typically answer questions quickly about most of the common features in the handheld application. However, when asked about the more complex aspects, it took me a few minutes to "page swap" the handheld code into my brain. :)