How much of washed yeast to use in next batch?

I washed yeast for the first time on my last batch and I'd like to try and use it for my next one. I've read that people usually split the washed yeast into several mason jars. Then they'll make a starter with one of the mason jars.

However, I just have it all in one growler. If I used the entire growler for a starter would I have too much yeast for my starter? Could I possibly just use the whole growler and not even make a starter?

For what it's worth, the washed yeast is wyeast 1056 from a 5 gallon batch and I plan on my next batch being only 3 gallons.

Thanks for the help!

How old is the washed yeast?
If it has been in the fridge >1 month than make a starter, there will be a lot of dead yeast cells.

There are some calculators like mrmalty that can help calculate how much yeast to use.

It's 4 1/2 weeks old and I probably won't brew for at least another week or two.

I made up this calculator (you might have to copy it to your Google Docs to edit it) and I'd love some feedback from anyone to make sure I'm on the right track.

You enter all the things in grey if you have them and you'll see how many yeast cells you have. Then you'd enter that value in yeastcalc.com to see if you need to make a starter for the particular beer you are making. Hope that helps.