It ignores all preexisting pensions, be they personal, corporate or state unless you decide to actively include them, (see the numbered notes).
Charges are fixed at 1% pa management, as per Stakeholder. Your actual charges may be different.
Growth is fixed at 7% gross, inflation at 2.5%.
(1) If you have existing pensions funds for which you know the current value, you can include these. Eg existing personal pension of £100pm is worth £10000 and you are thinking of a single premium of £5000, put £15000.
(2) If you have existing pensions funds for which you know the current value, you can include these. Eg existing personal pension of £100pm and you are thinking of an extra £150pm, put £250.
(3) Target income is your ideal pension income in todays terms. The calculator ignores State Pensions so bear in mind that these will ADD to your income. Of course State Pensions may change, but assuming the status quo:-
A Single Persons pension is circa £3900pa (and can be claimed by both members of a married couple if they, as individuals, have a sufficient National Insurance record). In couples where one person qualifies and makes a claim for a Dependents pension the couple get circa £6240pa.
EG - A DINKY couple (Double Income, No Kids Yet - and planning to both maintain their careers even if they do have kids) who want to retire on £18000pa should put a target income of £10000 because they will be getting circa £8000pa in State Pension, taking them up the £18000 they want.