Class skill +3, when you have 1 rank in that skill

Question

"If you select a level in a new class, all of its class skills are automatically added to your list of class skills, and you gain a +3 bonus on these skills if you have ranks in them."

I'm confused here... It tells that class skills are automaticaly added to my skill list with bonus +3, but then I must have a rank in that skill, what does it mean?

When I want any class skill, I must invest one skill rank, and then I will have the +3 bonus, which means I will have +4 + ability modifier? What if I want to invest all of my skill ranks in non-class skills? Will I have these class skills with +3 bonuses?

Answer 1

You are correct that class skills automatically get a +3 bonus when you put that first rank in it. However, non-class skills do not get that same bonus. To put it down as a formula...

Class skill bonus = Attribute Modifier + Ranks (1/level max) + 3 (but only if 1 or more ranks are in it)

Non-class skill bonus = Attribute Modifier + Ranks (1/level max)

Edit: However, when you multi-class, you do gain all "class skills" from the new class to your list of class skills, allowing you to retroactively gain the +3 bonus.

Answer 2

I'm not sure where you're drawing that particular quote from, but here I found a good explanation of how it works. I'll quote the whole thing at the end, but first the quick summary:

• A skill is considered a class skill for you, if it's on the class skill list of any class you have levels in.
• You get a +3 bonus on checks with any class skill in which you have invested ranks.

Each level, your character gains a number of skill ranks dependent upon your class plus your Intelligence modifier. Investing a rank in a skill represents a measure of training in that skill. You can never have more ranks in a skill than your total number of Hit Dice. In addition, each class has a number of favored skills, called class skills. It is easier for your character to become more proficient in these skills, as they represent part of his professional training and constant practice. You gain a +3 bonus on all class skills that you put ranks into. If you have more than one class and both grant you a class skill bonus, these bonuses do not stack.

Answer 3

Let's see what happens by tinkering a bit with an example character. We have, let's say, a first level warrior. This warrior has

• 1 rank in swim, which is a class skill
• 1 rank in climb, which is a class skill
• no ranks in jump, which is a class skill
• 1 rank in use magic device, which is a cross-class skill
• no ranks in tumble, which is a cross-class skill

He gets a +3 bonus in swim and climb, because they are class skills and he has purchased at least one rank in them. He has no bonus in jump and tumble, because he has no ranks in them. He has no bonus in UMD and tumble, because they're not class skills.

Now he levels up and takes a rogue level. He puts 2 skill points in jump.

Being both rogue class skills, tumble and UMD are now class skills for this character too. He now gets the +3 bonus on UMD, since he has a rank in it. He also gets the +3 bonus on jump. He would have gotten this even if jump wasn't a class skill for rogues.

The number of ranks you invest is irrelevant, as long as it's at least one.

So if your warrior/rogue puts all his ranks in a cross class skill for both classes, he does not get the +3 bonus.

I think the confusion comes from this sentence of yours: It tells that class skills are automaticaly added to my skill list with bonus +3

No, it doesn't do that.

Your class skills are not the skills with the +3 bonus. It's the list of skills that can get a +3 bonus, provided you buy a rank in them.