According to the PHB:

It would take 41.6 days to travel 1000 miles at a normal pace.
It would take 4.16 days to travel 100 miles at a normal pace.

By adding 1 mile to the daily travel time this gets simplified to:

It would take 40 days to travel 1000 miles at a normal pace.
It would take 4 days to travel 100 miles at a normal pace.