Minecraft wiki entry for Legacy_village_mechanics, associated text: Village Info mod by trunkz - The mod provides a more detailed look at what's going on with your village. It adds a few lines to your F3 screen indicating if you're in or near a village, and info about its size, population (both current and maximum) number of houses, etc.
Imgur gallery by Derrick - A briefer, more compact visualization of what makes a "house," and a bonus "villager breeding unit" that can support up to 35 villagers in an 11×10 or so space (the unit takes up that much space, the villagers themselves wander around outside of it)