How many Terran Marines can a Protoss Zealot take on in Starcraft 2?

This is assuming that neither of the units has been upgraded and neither is being healed. Also assuming that all of the marines attack at once and it is a fight to the death.

Using a unit tester, assuming both groups are moving towards each other using attack move, no upgrades, no microing, and that all marines are grouped up, the max that I could take out was 3 marines with 1 zealot with 7 hp left, if all 3 marines are spread out with some small space between each unit, zealot survives with 2 hp most of the time.

A little marine micro and the zealot will die to 3 marines with 1 or 2 left.

4 marines constantly destroy the zealot.

So the problem with this equation is that Marine DPS increases proportional to the number of marines. However, Zealot DPS increases proportional to the surface area of the Marine "ball." So while 1 Zealot can take down 2-3 Marines, 200 Marines will crush 100 Zealots.

If you can find yourself a nice enough choke, you can probably handle 100 Zealots with 150 Marines.

So there is no good rule of thumb here for ratios of Zealots to Marines.