What is Spell DC?
My group is new to table top RPGs, and one thing we haven't figured out is Spell DC.
One player was a cleric, and channel energy does force the undead monsters to make a saving throw, but I don't think that is Spell DC. So what is Spell DC, and what does it do? Does it mean the enemy can do a saving throw against the DC to determine whether the spell hits? If that's the case, does melee or ranged attacks have a similar DC?
I did a simple search that told me Spell DC is calculated by spell level + 1/2 class level + WIS for cleric or INT for wizard. Is that right?
No, there is not DC for melee/ranged attacks. Generally, each attack/spell gets one d20 roll. Either by the attacker to hit a target number (melee, range, & touch attacks/spells) or the defender to resist the effects of the attack (saving throws against spells and abilities).
Spell DC is a property of all spells, but usually only comes into play when the spell has a saving throw. You see saving throws mostly on spells that do not have an attack roll. These spells usually automatically hit, but give the target a chance to overcome some or all of the spells effects by making a saving throw. The DC of the spell is the target number for the saving throw.
To calculate the Spell DC:
10 + spell level + ability modifier (e.g. Wizards use INT, Clerics use WIS, Bards use CHA)
Spell DC differs from the DC related to Ex (extraordinary) and Su (supernatural) abilities, like the Cleric's channel energy ability. To calculate the DC for these abilities use the formula:
10 + 1/2 level + ability modifier
It should be noted that the Spell DC is only relevant for spells that have a Saving Throw. This will be in the stat block for the spell. See http://www.d20pfsrd.com/magic#TOC-Saving-Throw
DC stands for difficulty class. Anytime your character performs an action that doesn't have a guaranteed success, you need to check (usually skill) for success. The result of the check has to be equal to or greater than the DC of the action being performed to succeed.
The calculation for a spell is 10 + spell level + ability modifier. To clarify for spell use - This is what establishes the DC for the save of the spell. This is what the target of the spell has to meet or exceed to qualify for any saves (Such as half damage or similar).
DC Stands for Difficulty Class, and it represents the difficulty in either resisting, avoiding, or succumbing to the effects of a spell. When a spell lists in its descriptions that it requires a "Reflex Save for half" or a "Fort Negates" it means that a Save against the Spells DC must be rolled to avoid the effects of the spell.
In the case of "Reflex Halves" if a character succeeds in a reflex save against the Spell DC, he takes half damage from the spell effects as he's able to avoid the explosion, only get hit by part of the lightning bolt, etc.
If the case is "Fort Negates" it means that the effects of the spell are negated by a successful Fortitude save against the Spell DC. Spells like Poison have effects which you must shrug off with your body instead of your feet.
To calculate your Spell DC use the following Formula:
Spell DC = 10 + Spell Level + Primary Casting modifier ( INT for Psions and Wizards, CHA for Sorcerer's and Bards, WIS for Druids and Clerics )
An interesting thing to note is that you can use the feat Heighten Spell to prepare a spell in a higher level spell slot, which will in turn Increase the Spell DC. For example, with a spell like Glitterdust which is a second level spell, you could prepare it as a 5th level spell to increase the spell DC to make the effects harder to resist.
Alongside spells are also Spell-like abilities which have the (Ex) denoting Extraordinary abilities, or (Su) which indicates a supernatural ability.
The formula for the DC of those spells is slightly different, and is calculated with your level instead of the spells level.
Ex / Su Ability DC = 10 + 1/2 Level + Specified Ability Modifier ( For clerics Channel energy, this is CHA )
The Specified ability modifier can often be found in the ability description of the ability, such as the one for Channel Energy.