Starter size vs flask size

Probably a dumb question, but if I put a 2L starter into a 2L flask, am I going to make a mess? I don't want to lose any yeast or clean up a mess

yes, because you'll be at the brim of the flask, so when it starts bubbling...mess.

Not to contradict, but if its an erlenmeyer (spelling?) flask then the graduated portin stops well before the neck turns straight. I do 1000 ml starters in my 1000ml flask and have never had it bubble over.

Thats what I thought. So maybe scale down to 1500? I'm making East India Pale Ale tomorrow for big brew day and this is my first starter. Recipe calls for 3 packs/vials of yeast. I forget what the calculation was for starter size.

I do 1800 to 2000 ml in my 2000 ml flask, but I always use one drop of foam control (the 5-Star product, basically the same as FermCap).

Is your flask graduated? I.E. lines that tell you how much volume is in it? Maybe grab an old 2L soda pop bottle and check to see if 2L actually fills it to the brim? Also, you may want to invest or make a stir plate (made mine for $10). The stir plate will help to keep the foam down.

Calc said 1.6 L starter so I'm good anyway. It is graduated, but it says approximate. My wife just read in cooks magazine the other day that Pyrex measuring cups were quite inaccurate (we're both chefs) and now I don't really trust them (and my flask was slightly off by my measuring cup anyway. )

Yeah, before I got the stir plate mine would foam up pretty good, but the stirring motion keeps the krausen down (for everything but my 3068 starter). I can generally fit a full 2L in a 2L flask with the stir plate without a problem since my 2L mark is at the bottom of the upwards curve. However, I also generally boil in a separate pot and pour into the sanitized flask once its cooled, not sure if I would try to boil 2L of wort in a 2L flask without some fermcap.

I do have a homemade stirplate. Just got my stirbar a few days ago, and they didn't want to work together, tried to modify my stirplate and got a regular ole snafu. I got it working again though.
I thought about boiling in the flask, but I need my starter, so not taking any chances.