Calculating winrate at HU SnGs

[Fubster]

I was going to post this in the beginner's section, but I felt I'd get the type of responses I'm really looking for here.

Question from someone who is still learning HU SNGs:

What's the easiest way to calculate your winrate? I've just been sharkscoping myself and looking at my 1-on-1 numbers thru there.

Also, how many games should you put under your belt until you can be confident in your numbers? How do the HU shootouts (4 person, 2 heats, winner-take-all) affect my winrate etc?