D&Dtools

When you cast this spell, you grow to Huge, Gargantuan, or Colossal size, depending on your caster level.
Your Strength, Dexterity, Constitution, natural armor, size modifier to Armor Class and attack rolls, and space and reach all change as shown on the accompanying table.
(You need not assume the largest size you are capable of; you can choose to grow only to a smaller size if you wish).
All your equipment changes size with you, allowing you to use weapons or magic items effectively in your giant form.
See Table 2-2: Increasing Weapon Damage by Size, page 28 of the Dungeon Master's Guide, to determine the damage dealt by any weapons carried when you cast giant size.
Material Component: The scale of a dragon or hairs from the head of a giant.