How to count distinct values in a column

I have a spreadsheet which contains (see illustration below)
1. a column called LEAD ID which contains a unique id
2. a column called WON which signifies if the deal was won/not won (1 = WON, blank = Not Won)

I can have multiples of the same value in the Won and Unique Id field (see illustration below)

I would like to create a formula field which returns the summary of the No. of Deals WON
I need to tie the formula back to the Lead ID and whether or not the WON field contains 1 or not.

I've tried this formula but it won't work
(Lead ID is in Column A, WON is in column B)

=IFERROR(SUM(1/COUNTIF((A:A,A:A) AND(B2=1)),"0")

LEAD ID WON No. Won (Formula field)
abc112 0
abc222 1 .25
abc222 1 .25
abc222 1 .25
abc222 1 .25
abc333 1 1
abc444 0



Any help would be greatly appreciated
Thanks

I'm not using a filter because I want to use the output of the formula in a pivot table which will be used by Sales People

Daddylonglegs: I tried your formula but it does not work for me

Sean Thomas: Here's an illustration of what I'm trying to achieveWonFormulaField.jpg

Daddylonglegs: I tried your formula but it does not work for me

Sean Thomas: Here's an illustration of what I'm trying to achieve WonFormulaField.jpg

Thank DD that worked a treat