Pension Calculator

Just found this site today - it looks great! This is my first post so forgive me if its a basic one.

Are there any rules of thumb/calculators to help you work out what % of salary you should be aiming to provide for as a pension. Obviously it will vary per person and depend on lifestyle etc but assuming mortgage and loans are paid off what should a person aim for? Would it 60%? 50% of salary ??

Any help would be appreciated

There is at least one pension calculator listed here in case that's of any use.