Maybe you'll find this useful. I think it's from an earlier edition of the Renaissance PoW rules.
Tercios = 1,500 to 2,000
Infantry = 750 to 1,200
Skirmishers = 250 to 500
Mounted / Cavalry = 500 to 750
I looked at the lists to come up with a Fornovo at 40 points per side – with an approximate strength using the above as a guideline.
French:
CinC: (12 pts / 52 strength) – 4 mounted (3,000)
Swiss: (13 pts / 56 strength) – 4 pike (3,000) (from the Swiss list)
Main: (11 pts / 61 strength) – 1 artillery, 3 arriere bans, 1 skirmish foot (3,500)
Optional: (4 pts / 26 strength) – 2 mounted (1,500)
Total: (4o pts / 195 strength) – 16 units (11,000)
Italian:
CinC: (10 pts / 46 strength) – 2 mounted, 2 foot, 1 artillery (4,000)
Van & Main commanders: (6 pts)
Pike option: (8 pts / 50 strength) – 5 foot (6,000)
Mounted option: (8 pts / 46 strength) – 4 mounted, 1 skirmish mounted (3,500)
Stradiot option: (4 pts / 40 strength) – 4 skirmish mounted (2,000)
Foot Crossbow option: (4 pts / 40 strength) – 3 foot, 1 skirimish foot (4,000)
Total: (40 pts / 222 strength) – 22 units (19,500)
If, one used a 1,500 per foot on the Italian side it would be a total of 22,000. Close enough. Although the above list only has about 4,500 mounted for the French.