Warp factor is a measurement of warp speed. A warp factor of 1 is equal to the speed of light.
In the 24th century the warp factor scale used by the Federation was adjusted making Warp 10 the theoretical maximum. It was believed that at Warp 10 an object would be travelling at infinite speed and would inhabit all points in the universe simultaneously. (VOY: "Threshold")
External link[]
- Warp factor article at Memory Alpha, the canon Star Trek wiki.