Remember, your partner is only eligible for a pension if you both meet certain conditions.
Working out the value of the pension for your partner if you die is not straightforward, to give you a rough idea, they get 160th of your pay for each year of membership. In other words:
Current members: the membership is based on the period from the date you joined right up to your normal pension age.
Deferred members/pensioners: the membership is based on the length of time you paid in for with no enhancement.
Further rules apply, especially if you form a cohabiting partnership after you leave.