How does 2-handing a weapon affect damage?

I imagine this answer might get complicated depending on how the weapon is infused and which stats scale it, but maybe not. Obviously, I don't really understand how one-handing vs two-handing affect things. In previous games, I've used Strength-scaling weapons and 2-handing had an obvious effect. How about if I'm using a fire-infused weapon, though, which removes scaling?

I'm curious about all the ways 2-handing affects damage, but most specifically how it affects weapons that don't scale with strength.

Solution 1:

Two-handing a weapon in DS3 works a bit differently than in previous games.

The most important change is the addition of Weapon Arts, which, depending on the weapon, can do a great deal of damage, counter, or give versatility to your moveset. In any of these cases, your offensive potential is augmented.

Two-handing a weapon also can allow you to properly equip a weapon you do not meet the strength requirement for, as two-handing will add 50% of your strength towards meeting the requirement.

Lastly, for damage output, there is an increase, but it varies from weapon to weapon.

See this Reddit thread:

Name (Strength Scaling): 1H - 2H (% Increase)
Mail Breaker (E): 32 - 36 (12.5%)
Pontiff Knight Curved Sword (D): 119 - 138 (16.0%)
Hand Axe (D): 99 - 121 (22.2%)
Astora Greatsword (D): 128 - 157 (22.6%)
Irithyll Straight Sword (D): 120 - 145 (20.8%)
Longsword (D): 102 - 126 (23.5%)
Heavy Longsword (C): 107 - 134 (25.2%)
Sharp Longsword (D): 111 - 130 (17.1%)
Raw Longsword (-): 96 - 101 (5.2%)
Broadsword (C): 112 - 137 (22.3%)
Great Club (C): 147 - 185 (25.8%)
Club (C): 90 -119 (32.2%)
Heavy Club: 110 - 140 (27.3%)
Reinforced Club (C): 94 - 123 (30.8%)
Butcher Knife (A): 90 - 127 (41.1%)
Deep Battle Axe (-): 104 - 111 (6.7%)

Solution 2:

In Dark Souls 1 and 2, rather than adding raw damage, you would gain +50% Strength when using two hands. Presumably the same thing happens in Dark Souls 3.

So for example, if your Strength was 10, then when two-handing, it would behave as though your Strength was 15. This allows you to two-hand weapons above your Strength, and adds more Strength scaling.

Solution 3:

Two-handing a weapon effectively increases your strength to 1.5 which allows you to wield a weapon with say a strength requirement of 30 at only 20 strength. Additional to this, the weapons damage is also increased at the same rate, but the stamina usage for swinging the weapon is also effected to 1.5

It's good to also note that some weapons (such as a longsword) have special attacks when two-handed that deal additional damage for the cost of FP.

Solution 4:

In my experience, 2handing ultra greatsword type weapons makes you do roughly 10% more damage.

Seems the lighter weapons are more damage-responsive to 2handing.