Some people charge by the meter. Personally, I couldn't be bothered carrying a tape measure round, so I pace it out and charge:
£2 a pace of guttering that's easily reached and
£3 a pace for guttering over a garage or conservatory that I have to reach sideways to get at.
That covers clearing the gutter and cleaning the outside = gutters, fascia and soffits.
Hint: do the job just after a heavy rain. It's MUCH easier and quicker.