Question: This is a mechanics question pertaining to the maximum allowed damage for the Paladin's *Divine Smite* ability.

> 
> **Divine Smite:** ...you can expend one [Spell Slot] to deal Radiant damage in addition to weapon damage. The extra damage is 2d8 for a
>  1st level slot, plus 1d8 for each spell level higher than 1st, to a
>  maximum of 5d8....
> 
> 
> 

**"...to a maximum of 5d8..."** is the part I'm having issues with figuring out how to rule.

Can the *extra* damage, beyond the 2d8 for filling a 1st level slot with the ability, be up to 5d8? Which would require a (Multiclass gained) spell slot of 6th level to add an extra 5d8 to the attack, making it 7d8 total (The default 2d8 + the maximum allowed extra of 5d8). *Or*, are the rules saying that the total allowed maximum damage can't exceed 5d8 total; which would only take a 4th level spell slot to add a max of 3d8 to the default 2d8?

2d8 + 3d8 = "to a maximum of 5d8" damage total?  

2d8 + "to a maximum of 5d8" extra total = 7d8 ?

My guess is the first choice, since without Multiclassing a Paladin can never have more than 5th level spell slots and could never have the 6th level slot required to add 5d8 to the attack. My PC differs though.

Answer: 
I believe the way it works is that by expending a 1st lvl spell slot gives 2d8, a 2nd lvl spell slot 3d8, a 3rd lvl spell slot 4d8 and a 4th lvl spell slot 5d8. a 5th lvl spell slot would also give 5d8.
If you multiclass to get higher lvl spell slots they would still give only the max of 5d8.
I've always seen it as being the additional damage beyond the 2d8 that is capped at 5d8. For example, a 20th level paladin has up to 5th level spell slots. As written, the damage progression is thus:
1st level slot - 2d8,
2nd level slot - 2d8 +1d8, 
3rd level slot - 2d8 +2d8, 
4th level slot - 2d8 +3d8,
5th level slot - 2d8 +4d8,

Why wouldn't they get to use their 5th level slots? I've always ruled at my own table that the 5d8 limit was for the bonus damage, meaning you can spend up to a 6th level on Smite, but nothing higher (For if you multiclass).