Can anyone tell me what level my paladin has to be to cast spells?

I found a formula that states: (Experience level - 5) / 2, with a maximum of 4, unfortunately I have no clue what this means. My math skills are as bad as my grammar.

Be level 7, as that's the level needed to reach spell level 1 according to the formula you posted.

4th level spells become available at level 13, but higher spell levels are not ever going to be available to your paladin or archer, unless there's some way to temporarily boost spell level.

Thank you. Why do they not just say level 7 for level 1 spells and similar spell progression as regular spell casters. The formula looks like "level 5 / 2" or to me level five divided by 2, hence the "/" which makes no sense it would be level 2.5 if you divide 5 by 2.

Anyway, thank you again.

The formula is for the highest level of spells you can cast at any given level.

In other words, take your current level, subtract 5, and then divide by 2, to get the highest level of spells your paladin (or archer) can cast.