Easy, normal and hard encounter for PCs

[Balor01]

So I am setting up an arena-style encounter for my PCs in which they will encounter the following:

5 Lvl1 Fighter kobold (CR1)
3 Lvl1 Scout kobold (CR1)
3 Lvl1 Cleric kobold (CR1)
1 Lvl1 Dragonborn Cleric kobold (CR1)

They play a Fighter, Cleric, Rogue and Wizard and i want for this party to face this group in a consequitive Hard/Normal/Easy mode by adjusting PC levels.

For an example:

if PCs are lvl 6 encounter is easy
if PCs are lvl 4 encounter is challenging
if PCs are lvl 3 encounter is hard

I'd like to know your estimate on PC levels in order to get this right.

thanks

[Diarmuid]

The encounter calculator on the SRD (http://www.d20srd.org/extras/d20encountercalculator/)

pegs that as an EL 7.

That would make it "easy" for a party of 4 lvl 7's, hard for a party of 4 lvl 5-6, and difficult for a party of 4 lvl 4's. This assumes normal optimization.

[Chen]

That many low level creatures are going to get disproportionately easier as the PC level increases. At level 5 and above the Wizard could probably kill them all in one fireball barring evasion/resists. A black tentacles at level 7 would wreck them HORRIBLY. With such low enemy HP just winning initiative could turn the fight from challenging into super easy just from the first volley of ranged attacks without AOE.

[Balor01]

That many low level creatures are going to get disproportionately easier as the PC level increases. At level 5 and above the Wizard could probably kill them all in one fireball barring evasion/resists. A black tentacles at level 7 would wreck them HORRIBLY. With such low enemy HP just winning initiative could turn the fight from challenging into super easy just from the first volley of ranged attacks without AOE.

Exactly. Thats why I aimed at 3-4-6 ratio.