It sometimes depends on the length of rail or size of rail.
Per D&RGW (ng) Standard plan: 39' rail= 21 1/4" ; per 33' rail = 22" ; per 30' rail 22 1/2" spacing.
Or 2981, 2880, 2816 ties per mile, respectively.
Trinchera Logging RR at Haskell, CO (Veta Pass) used 3520 ties per mile on 35# rail. (untreated, rejects and unsaleable ties)
It also depends on the traffic and weight of power that is run, causing variations to above.
You can get away with building anything you want for your own line and it would be correct.