When I dual cast a spell (casting with same spell in both hands):

  • How much magika will be consumed/needed to cast the spell (just the double of a normal one?)

  • How is the spell affected? (How much damage does it deal? Or how much does its heal?)

  • How are runes affected by dual casting? ("Trap"-Runes on the ground)

Of course given that you got the perk that allows dual casting in the school of magic you want to cast the spell.

  • pretty sure dual casting doesn't boost damage by 100%, but increases costs by 100%, which kinda stinks.
    – l I
    Nov 14, 2011 at 14:11
  • @yx. well there must be a benefit from it (except looking cool :P), if not the perk is kinda useless. But i think there is some damage increase. Or you atleast get the back-push benefit from the perk you can get after the dual cast one.
    – Lerkes
    Nov 14, 2011 at 14:15
  • there is a small damage increase and the impact perk bonus, that's all I've noticed so far. Its good for casting outside of combat for setting up traps and making conjurations last longer, but in combat I prefer to machine gun fireballs rather than casting big ones. I'm almost regretting spending 2 perk points in getting these.
    – l I
    Nov 14, 2011 at 14:19
  • 1
    @yx. well you can "stunlock" some enemys with the impact perk. Thats usefull sometimes. And i hope they put some kind of function in that you can unlearn a perk (for example using a dragon soul would be good).
    – Lerkes
    Nov 14, 2011 at 14:21
  • 1
    if no one answers by the time I get home I'll do some testing on this
    – l I
    Nov 14, 2011 at 14:32

7 Answers 7


How much magika will be consumed/needed to cast the spell (just the double of a normal one?)

It seems that dual casting cost a LOT more than just double the normal cost.

Single cast fireball - 42 magika
Dual cast fireball - 117 magika

Single cast chain lightning - 49 magika
Dual cast chain lightning - 137 magika

Single cast fire rune - 74 magika
Dual cast fire rune - 206 magika

Single cast conjure familiar - 44 magika
Dual cast conjure familiar - 122 magika

In all, looks like you will be using roughly 2.8x the magika cost of the single cast spell.

How is the spell affected? (How much damage does it deal? Or how much does its heal?)

For conjuration spells, dual casting doubles the conjuration life span of the spell.

For destruction spells, here are some damage values:

I used Cicero as my dummy target since its always fun beating up a clown.

He started out at 375 health (you can see a NPC's health by selecting them via the console and typing in getav health). You can also use this to see every other skill/stat of theirs. I avoided fire spells since they can burn and throw off some numbers with its burning damage.

Single ice spike: 25 damage (exactly matches the expected value I see by selecting the spell)
Dual ice spike: 55 damage

Single lightning bolt: 25 damage
Dual lightning bolt: 58.23 damage

Overall, it looks like damage is increased by roughly 220%

Keep in mind that impact will knockback the target if you get the perk.

For any other duration spells, the duration is doubled as well but the effects remain the same (stoneflesh still boosts armor rating by 60).

Dual casting the ward spells doubles the armor bonus.

How are runes affected by dual casting? ("Trap"-Runes on the ground)

1 handed Frost rune damage: 50 (matches expected value)
1 handed Frost rune attempt #2 35 damage
1 handed Frost rune attempt #3 22 damage (lol)

2 handed Frost rune damage: 64
2 handed frost rune attempt #2 55
2 handed frost rune attempt #3 75

The damage is not quite doubled, but the damage itself from the rune varies greatly due to the location of the rune and how close the target is to the center. Its entirely possible the rune damage is also doubled, but its very rarely that you actually hit for the max amount.

  • Thanks for the testing. This means that the perks arent really worth it...(except for conjuration i guess). But i'd like to have the correct numbers. (just out of curiositiy :D) Maybe we get some mod or some DLC/patch that allows to see the effective numbers somehow.
    – Lerkes
    Nov 15, 2011 at 7:58
  • yea, I thought there was a console command to show stats for the target but I couldn't find it
    – l I
    Nov 15, 2011 at 10:39
  • Yes that is something that would Give insight..... Maybe there is a command that lists all commands or something... Ill have a look on it. But sadly its Not possible to scroll in the console AFAIK.
    – Lerkes
    Nov 15, 2011 at 10:49
  • @Patrick you use page up and down to scroll in console
    – l I
    Nov 16, 2011 at 1:17
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    I used Cicero as my dummy target since its always fun beating up a clown. LOL +1
    – o0'.
    Nov 22, 2011 at 13:29

In terms of the AOE on spells such as Fireball, it seems like the surface area of the blast is, indeed, doubled. It just doesn't look like it due to geometry, but the AoE of a 15m diameter blast would be doubled with something like a 21m blast. Surface area increases with the square of the radius, so 1.4 times the radius doubles the surface area. That said, dual casting fireball feels like overkill for me,but the knowckback effect of the Firebolt, Ice spear, etc. is rather effective.

  • 1
    Hunh. Never thought of the Surface Area doubling instead of just the radius. Nov 15, 2011 at 23:53
  • interesting... doubling surface area does sort of make sense
    – l I
    Nov 16, 2011 at 12:48

I've played around with this a bit, and it does appear that spells do more damage when duel-cast rather than 2x single cast, but not by a lot. It's hard to judge since I don't have numbers on the enemy health though.

I saved my game so I can re-load and try over on the same enemy to use as a control, and while it died in a single duel-cast ice spike, it had maybe 10% hp left when I just hit it with 2 single cast ice spikes. Again, it's really hard to judge with no numbers, but it does appear to boost damage, at least by a little.

As for magika use, it seems to cost roughly 3x the amount of magika compared to a single cast. It seemed to fluctuate for me between 2.7 and 3.1 depending on the spell. You can see this as well with the other answer above listing the magika cost (fireball for example, 117/42 = 2.8).

So it looks like it basically does 2-and-a-bit times as much damage, but costs 3 times as much magika. This would result in a slight boost in damage per second, but a drop in damage per magika. Combined with the impact feat, it seems to be useful situationally.

I haven't tested healing at all, so I can't comment on that.

Duration spells are simply doubled. That one was fairly easy to test. Armour spells and such don't appear to boost your armour any more than a single cast would.


yx's conclusions are accurate. According to modders who have examined (and altered...) the relevant game settings, dual casting in vanilla/unmodded Skyrim multiplies magicka cost by 2.8, spell effect by 2.2, and casting time by 1.0.

  • So, I'd say, a bit sketchy before you've gotten your mana recover and pool leveled up a bit, but it does kill stuff faster, so worth it eventually (also the stagger effects and such).
    – Svish
    Jan 25, 2017 at 22:56

It depends largely on the traits you get from leveling up: dual cast on summoning make them last longer, destruction increases the damage or effect, or both, such as a spell that deals fire damage and leaves the target burning. It may damage more and leave the target burning longer... stuff like that.

  • Yes i read the description of the perks already. But I want to know it more exactly how the spells are affected. Because it seems its not just "doubled" see the answer from yx..
    – Lerkes
    Nov 18, 2011 at 22:01

You are all forgetting something really important about destruction dual casting : combined to the impact perk, it allows you to be almost invincible. As long as you have a sufficient amount of mana (mana is not a problem for a full mage, it is easy to get apparel that reduce your mana cost by 100% or to have an overall 300% increase of mana regeneration), the dual casting perk + impact perk allow you to CONSTANTLY STUN ALMOST EVERY FOE of the game (it works against dragons, bosses, even Alduin, just doesn't work against foes who use a ward). Since I've got the impact perk, no foe has ever been able to hit me, except mages (or when they are in group, I obviously cannot stun anyone). So yeah, the dual casting perk is useful if you intend to also unlock the impact perk, which is in fact one of the best perks in the game.


I believe dual could be interpreted as Double, I currently use dual with my destruction magic up to 20% on Dual Casting which is stronger then any weapon I currently have.

With no knowledge gained form schools or anything. I also sure double healing which heals 10x quicker then one handed. I relive it all depends on personal habits in the game.

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