How do the weapon stats scale per upgrade?

I've noticed that the higher the number, the more value is added per upgrade. I.e. a weapon with 250 base damage gets more per upgrade than a weapon with 25, but does anyone have the exact formulas? I'd like to be able to figure out how much damage a fully upgraded weapon is before spending a ton of mana on it so I can compare it to my current weapon more easily.

Also, having the elemental damage formula would be nice too, since it seems to raise at a faster rate than physical damage.

Solution 1:

Did some lab work in the tavern with a squire. What I've found is that physical damage upgrades to 1.15 of previous damage. Elemental upgrades to 1.20 of previous damage. Physical upgrades seem to cap off at 80 per upgrade whereas elemental damage seems to be capped at 300ish.

As a general way of estimating weapon damage for upgrades:

• For physical damage, every 5 upgrades doubles the amount
• For elemental damage, every 4 upgrades doubles the amount

A 50 base physical weapon with 20 upgrades will end up at roughly a final stat of 800 (818 to be exact).

Damage per hit depends on your class and the attack stat of your character.

For the squire, the 2nd strike in the combo is at 1.20 of the base damage, 3rd and 4th are at 1.40.

I'm currently unsure of how hero strength factors into this. I originally thought it was .03 phys damage added back per point, but that is mistaken. My weapon of 432 on a squire with 46 str does 848 dmg which is 1.962 repeat damage, divided by my str thats a modifier of 0.042 added per Str point, but my squire with str 74 and sword 58 dmg is doing 129 so 2.224 damage, which when divided by str is 0.03 per point.

I'm assuming that each str point has less of an impact on a curve but the formula I don't know.

Solution 2:

There is a cap to each of the stats PER upgrade, weapon base damage caps out at 80, projectile speed caps at 1200 so on and so forth. From what I can see the hero damage is minimal. I was playing with a huntress in mythical gear [PC]

611 hero damage & 3872 weapon base damage provided 15890 per hit
612 hero damage & 3872 weapon base damage provided 15898 per hit
612 hero damage & 3952 weapon base damage provided 16227 per hit
613 hero damage & 3952 weapon base damage provided 16236 per hit
614 hero damage & 4032 weapon base damage provided 16573 per hit

You can see that as the weapon damage goes up, the additional damage added per point of hero strength goes up. It looks to be a fractional percentage.

In the first case, the damage per hit was 4.1038~ times the weapon damage. 
In the second case, with one more point of hero damage, the damage per hit was 4.1059~ times the weapon damage.

EDIT: Somehow I missed the accepted answer so all of this is superfluous.

Solution 3:

I made an Excel formula to figure out Dungeon Defender Weapon Damage. You can find it here; if you want to save it, just click the link and select File → Download.