Wagons needed for a typical 60,000 Union/Confederate Army computed as follows.
Assume each wagon using had a 4-6 Mule team and could haul 1,500 lbs over rough roads.
1) Backup ammo. Each man carried 40 rounds weighing about 5 lbs. Usual backup reserve was also 40 rounds each per man. Accordingly, each wagon could carry ammo for 300 men. An army of 60,000 infantry needed about 200 wagons for rifle ammunition.
2) Artillery. 60,000 men would require at least 3 artillery pieces per thousand or 180 guns. Each gun would require a caisson (50 rounds) and wagon (100 rounds) total wagons/caissons = 360 + 40 wagons for forge and blacksmith, vet, etc. = 400 total. This is conservative, since Lee at Gettysburg had 4 guns per thousand with 250 rounds each.
3) Each regiment (estimate 300 men) would require a wagon for a surgeon, hospital tent and medical supplies = 200 wagons.
4) Each regiment would require 1 wagon for officer baggage, feed for officer horses, tent/table for the Col., cooking supplies, band instruments, entrenching tools, etc. = 200 wagons
Total 1,000 wagons/caissons and 4,000-6,000 horses and mules for a 60,000 man army. This does not include wagons for food or horse ambulances or extra feed for the mules. Also, this is approximately 16 wagons per 1,000 men. This seems the bare bones minimum, since Lee had 30 wagons per 1,000 men while Sherman on his march to the sea had 50 wagons per 1, 000 men.