[Tade0]

a professional developer will write on average 10 lines of code (LoC) day.

My experience so far is a team of developers can deliver 30-100 LoC per day of front-end code.

The team size is of little consequence. It's been hilariously consistent across projects and companies I've been in.

[Insanity]

That's a pretty big range - but I'd say frontend code tends to be faster / take up more lines. Center a button, give it a colour, make it responsive and you've probably reached your 30 lines of HTML/CSS :P

[nudpiedo]

but the fine tuning, bugs and corrections, reported issues and other aspects should be part of the metric too. The days were there i barely progress because some alignment is not working and coordination with the design team is taking the time makes it part of the average as well