I did a quick search for the calcium value and it will be hard to reach what is available in store milk (which are themself boosted with additional calcium).
Two cups of homemade almond milk would provide roughly 50-60 mg of calcium as opposed to something like 300mg in regular milk or commercial soy/almond/rice milk.
I guess an important point would be the ratio at which you make your almond milk (almond:water). Being said that 20-25 almonds are about one once. Since most recipes I've seen suggest 1:3 ratio almond/water, that would be 1 cup of almond for 3 cups of water and considering there are 8 onces in a cup and that one once of almond contains about 75mg of calcium then the whole liter would have about 600mg in it. But then again, you extract the nut "flesh" then probably don't get the whole calcium content (probably explains the 50-60 mg suggested before)... Considering that the suggested intake is around 1000mg, it takes a lot of almond to reach it.
That being said, if the point is to get your calcium, this might not be the best alternative. In order to avoid the other additive then it is, and well, might as well just take a calcium supplement on the side.