FREE: Rainbow Henna Hair Dye Ebony Black Or Dark Sable Choose One Or GIN For Both!

It depends on the thickness of the hair, but if your hair is longer than shoulder length you would probably use the whole jar. If you have short hair you could go half or a third.
A tip I learned from using henna a lot is to make sure to cure it for a full day before using it after its mixed up. And to mix it with an acidic liquid like coffee or tea with a squeeze of lemon. It also smells like cut grass and i usually add nutmeg and I've and allspice powder to it so it smells nicer. Henna stays on for hours (overnight is best) to deepen the conditioning and the color. (The color penetrates the hair shaft instead of laying on the surface mild other dyes) and so lasts longer than other semi permanent dyes. (Several months)
I have more tips and tricks which will be included for the winner. ;)
I hope that answers your questions-- and more.