There's been discussion on this before. A pace is roughly 3 feet.
Hi, This came out of a discussion on a different topic. it is sufficiently a tangent to not muddy up that post. A pace is defined, just not directly. True, there is no explicit statement saying that a pace is three feet; however, there are several unambiguous statements to that effect: On page 112, under the Duration of Sun/Ring, ArsM5 says: "A ring must actually be drawn while the spell is being cast....The magus may not move more quickly than ten paces per round (five feet per second) whil…