It's not quite as simple as just "1 mile."
When operating VFR in Class E or G airspace, the following tolerances must be applied to the planned tracks in order to avoid controlled airspace or restricted areas:
1-2000 AGL +/- 1 nm (day) +/-2 nm (night)
2000-5000AGL +/- 2 nm (day) +/- 3nm (night)
5001-10000AGL +/- 4 nm (day) +/-5 nm (night)
From 10001 to FL200 all VFR aircraft should apply +/- 8 nm