How would you evaluate project size?

Part A: Before you start a project.

Part B: For a complete project.

I am interested in comparing unrelated projects. Here are some options:

1) Lines of code.

• I know that this is not a good metric of productivity but is this a reasonable measure of project size?
• If I wanted to estimate how long it would take to recreate a project would this be a reasonable way to do it? How many lines of code should I estimate a day?

2) Function Points.

• Functions points are defined as the number of:
  • inputs
  • outputs
  • inquires
  • internal files
  • external interfaces
• Anyone have a veiw point on whether this is a good measure?
• Is there a way to **actually do this?

Does anyone have another solution? Hours taken seems like it could be a useful metric but not solely. If I ask you what is a "bigger program" and give you two programs how would you approach the question?

I have seen several discussions of this on stackover flow but most discuss how to measure programmer productivity. I am more interested in project size.