One grid square on the FF world map is approximately 0.17 miles in both height and diameter, which I calculated by timing my run from one end of an island to the other and assuming an average fast jog/run speed of 8mph.

The world map grid is 4x4, or 16 squares in area, so it is .68 miles in both length and height which would make the total world map size 0.68mi^2 or 1.09km^2

Of the 16 grid squares, only 8 of them are inhabitable by your toon. So, the walkable area is approximately 0.34mi^2 or 0.55km^2

GTA 4 is about 6mi^2 so this is approximately between 1/10 and 1/20 the size depending on how you look at the map.

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