Activate the F3 coordinates readout. Stand still and throw an Eye of Ender. Aim your cursor to follow the eye as it floats into the sky. Record your x and z coordinates, and your "facing" (the second number in the f: readout ) and type them into this page.
Where the lines intersect is the rough location of the stronghold.
In older versions of Minecraft (1.5?) there were three strongholds in
each world at roughly 120° separation when measured from the
world origin. The green annulus represents the range from 640-1152
which used to be the valid location for a stronghold.
While this math may govern the origin of the Stronghold, it does not strongly constrain the location of the End Portal (which is what the Eye of Ender points to) and since a Stronghold consist of a sprawling complex of (not always connected) rooms, the End portal can be outside the green annulus.
by Jennifer Reynolds and Robert Forsman
github project home.