Much like the "chalkboard paint" that you actually use chalk on, this stuff is out of my price league. (To make that, add grout to your latex wall paint.) How much??? I dunno... "some". I never measure, either.
The whole thing about chalk paint is that while it can be painted "perfectly", the beauty of it is to show all those character lines, dents and folds on the furniture that you already have or acquire 2nd hand. I guess its creator thought like I do, "Why hide its history? Like you, its life is what makes it beautiful. No 2 are alike."
Anyway, to make the stuff, you can add regular chalk to any latex paint. What happens when you do that?? You get a matte gesso. I'm not sure where you can get chalk at, probably online somewhere, but the deal is that ANYTHING really porous will work. Some people have used whiting (can't find that anymore), cornstarch (I've used that successfully myself) and plaster of paris (has been used for fresco painting for hundreds of years- the paintings themselves last hundreds of years, too, so you know this stuff is good).
I do know that cornstarch will NOT change your paint color at all, but will
1. increase adhesion: so you won't need to use a primer, either
2. make your paint matte (like chalk paint)
3. increase porosity (which increases adhesion, etc.)
I did not use primer under the stuff I made and it stuck like crazy. I wopped it in a few places, tried to chip it and it won't come undone.
My next batch will have plaster of paris in it... and I'll post pictures. Note: be careful to only add a little to paint you intend to use because this stuff will set up and get hard to use! Please remember that, I don't want you wasting paint, time or money.