So here is one formula, it gives the distance traveled at a constant G, but the time is in stationary framework time, so I don't yet know what shipboard time would be but here goes: (All units must match of course)
ST = stationary framework (Earth framework)
D = distance traveled in ST
C = speed of light
A= acceleration in ST
T=time in seconds.
D= C*A*T^2/ (C+Sqrt (C^2+A*T^2))
So with a constant A of 1 G, it says after 10 years earth time the ship has covered 31 light years, so if you consider that half the trip, then reversing accel to decel at one g puts you at twice that distance in twice the time, so 10 years of accel and 10 years of decel puts you 62 light years down the road. Not sure what the shipboard time would be however.