Warhammer unit sizes?

[Brian]

Small units of ranged troops benefit from being only two deep. Thunderers work best this way. Larger units, such as Wood Elf Glade Guard, are often used in deeper formations, as they can usually volley fire. In most armies, really wide ranged units are a bad idea, as they can be cumbersome to maneuver and are killed easily once engaged in close combat.
With melee oriented troops, such as Warriors, the real question is what are they fighting against? Generally, this will be similar troops ranked up 5 wide. With 20mm bases (the smaller ones), you will either want to go 5 wide to minimize casualties, or 7 wide to maximize offense. For troops on the larger, 25mm bases, 6 wide is pretty much ideal.
Keep in mind that you can reform your units during the game. If your 10 wide Thunderer unit is about to be charged, you can just form up 5 wide (during your movement phase) and have double the ranks of bonus.

tl;dr - Thunderers/Quarrelers = 10, Warriors = 28 (assuming you mean Dwarfs).