My most productive day of coding ever involved writing (wait one second) 119 lines of code, counting comments and white space. But they were the right lines, because they improved the experience of my customers and are making me an absolutely sick amount of money for the amount of time invested.

We're not factory workers -- mass is not a good metric of productivity.

What is a better metric?

1. Number of people happily using your code. 2. Number of dollars in your bank from it.

"Perfection is reached, not when there is no longer anything to add, but when there is no longer anything to take away." -- Antoine de Saint-Exupery

Goals accomplished. Its vague, but if you're at a startup (or coding for fun / to learn), perfect. Goals can be bugs squashed, features added in, performance gains, whatever you need. Its yours to mold when you start for the day and destroy when you end for the day.

If you're at a more established company, then chances are, they'll care about things getting done, but on a day to day basis, will have a different metric to use. Which is the angle you're coming from, I think.