SPECIAL THANKS TO

IsharaMeradin, whose know-how and help proved greatly valuable for the creation of this mod.

What does this mod require?

The most current version of the Skyrim base game, the Dragonborn DLC and the Dawnguard DLC.

What does this mod do?

In one sentence: Gives you a spell that will convert your low damage arrows over to the highest damage arrow types you're carrying in your inventory.


In detail: 
If this mod is loaded when you start up your game, you will automatically receive a spell called 'Arrow Conversion'. This spell costs no mana and can be cast instantaneously. When cast, the spell activates a script that (1) checks what the highest damage arrow in your inventory is, and then (2) converts lower damage arrows over to that highest damage arrow type according to a conversion rate for that specific arrow, then (3) checks what the second highest damage arrow in your inventory is, and then (4) converts lower damage arrows over to that arrow type according to a conversion rate for that specific arrow type, etc. until it can't detect and convert anything else.

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What arrows are affected (as you can see, some arrows share the same damage rank):

Forsworn Arrow (base damage 7)
Falmer Arrow (base damage 7)
Iron Arrow (base damage 8)
Steel Arrow (base damage 10)
Ancient Nord Arrow (base damage 10)
Riekling Spear (base damage 10) [Dragonborn DLC]
Orcish Arrow (base damage 12)
Dwarven Arrow (base damage 14)
Nordic Arrow (base damage 14) [Dragonborn DLC]
Elven Arrow (base damage 16)
Bloodcursed Elven Arrow (base damage 16) [Dawnguard DLC]
Sunhallowed Elven Arrow (base damage 16) [Dawnguard DLC]
Glass Arrow (base damage 18)
Ebony Arrow (base damage 20)
Stalhrim Arrow (base damage 20) [Dragonborn DLC]
Daedric Arrow (base damage 24)
Dragonbone Arrow (base damage 25) [Dawnguard DLC]

Note:
If you have an arrow in your inventory that isn't one of these (which would be a rare occurrence), it can't be converted to or from.
If you have only one arrow in your inventory, there won't be anything for the script to convert.
If you have only arrows with the same base damage in your inventory, there won't be anything for the script to convert.
If you don't have enough low damage arrows in your inventory to turn into another arrow type, there won't be anything for the script to convert.

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What are the conversion rates:

1 Dragonbone Arrow = 1.04 (25/24) Daedric Arrow = 1.25 (25/20) Ebony Arrow (or Stalhrim Arrow) = 1.39 (25/18) Glass Arrow = 1.56 (25/16) Elven Arrow (or variant) = 1.79 (25/14) Dwarven Arrow (or Nordic Arrow) = 2.08 (25/12) Orcish Arrow = 2.5 (25/10) Steel Arrow (or Ancient Nord Arrow/Riekling Spear) = 3.13 (25/8) Iron Arrow = 3.57 (25/7) Falmer Arrow (or Forsworn Arrow)

1 Daedric Arrow = 1.2 (24/20) Ebony Arrow (or Stalhrim Arrow) = 1.33 (24/18) Glass Arrow = 1.5 (24/16) Elven Arrow (or variant) = 1.71 (24/14) Dwarven Arrow (or Nordic Arrow) = 2 (24/12) Orcish Arrow = 2.4 (24/10) Steel Arrow (or Ancient Nord Arrow/Riekling Spear) = 3 (24/8) Iron Arrow = 3.43 (24/7) Falmer Arrow (or Forsworn Arrow)

1 Ebony Arrow (or Stalhrim Arrow) = 1.11 (20/18) Glass Arrow = 1.25 (20/16) Elven Arrow (or variant) = 1.43 (20/14) Dwarven Arrow (or Nordic Arrow) = 1.67 (20/12) Orcish Arrow = 2 (20/10) Steel Arrow (or Ancient Nord Arrow/Riekling Spear) = 2.5 (20/8) Iron Arrow = 2.86 (20/7) Falmer Arrow (or Forsworn Arrow)

1 Glass Arrow = 1.13 (18/16) Elven Arrow (or variant) = 1.29 (18/14) Dwarven Arrow (or Nordic Arrow) = 1.5 (18/12) Orcish Arrow = 1.8 (18/10) Steel Arrow (or Ancient Nord Arrow/Riekling Spear) = 2.25 (18/8) Iron Arrow = 2.57 (18/7) Falmer Arrow (or Forsworn Arrow)

1 Elven Arrow (or variant) = 1.14 (16/14) Dwarven Arrow (or Nordic Arrow) = 1.33 (16/12) Orcish Arrow = 1.6 (16/10) Steel Arrow (or Ancient Nord Arrow/Riekling Spear) = 2 (16/8) Iron Arrow = 2.29 (16/7) Falmer Arrow (or Forsworn Arrow)

1 Dwarven Arrow (or Nordic Arrow) = 1.17 (14/12) Orcish Arrow = 1.4 (14/10) Steel Arrow (or Ancient Nord Arrow/Riekling Spear) = 1.75 (14/8) Iron Arrow = 2 (14/7) Falmer Arrow (or Forsworn Arrow)

1 Orcish Arrow = 1.2 (12/10) Steel Arrow (or Ancient Nord Arrow/Riekling Spear) = 1.5 (12/8) Iron Arrow = 1.72 (12/7) Falmer Arrow (or Forsworn Arrow)

1 Steel Arrow (or Ancient Nord Arrow/Riekling Spear) = 1.25 (10/8) Iron Arrow = 1.43 (10/7) Falmer Arrow (or Forsworn Arrow)

1 Iron Arrow = 1.14 (8/7) Falmer Arrow (or Forsworn Arrow)

The logic is that, for example, a Dragonbone Arrow does 25 base damage whereas a Falmer or Forsworn Arrow does 7 base damage. Thus, damage-wise, you have (25 / 7 =) 3.57 Falmer or Forsworn Arrows for each 1 Dragonbone Arrow. 
That's the rate at which it will convert the lower damage arrow over to the high damage arrow - based on the relative damage difference between the lower damage arrow and the high damage arrow. 
Of course you can't actually put something like '0.57 of an arrow' in your inventory, so it will only convert in the nearest whole number.

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A few special conversion rules apply as well, depending on the highest damage rank that is detected in the player's inventory when the script starts converting. Some arrows are prioritized over others, and some are never converted to.

Rank 3: Steel Arrow, Ancient Nord Arrow, Riekling Spear (DLC)
The Riekling Spear has inferior velocity and range to the other arrow types and will never be converted to - if the player only has this arrow type as the highest damage one, then lower damage arrows will be converted to Steel Arrows instead. If the player has some Ancient Nord Arrows (but no Steel Arrows) as their highest damage arrow, then lower damage arrows will be converted to Ancient Nord Arrows. But if the player also or exclusively has some Steel Arrows in any capacity, then lower damage arrows will be converted to Steel Arrows.

Steel Arrow > Ancient Nord Arrow > Riekling Spear (NEVER CREATED)

Rank 5: Dwarven Arrow, Nordic Arrow (DLC)
If the player only has Nordic Arrows as their highest damage arrow, then lower damage arrows will be converted to Nordic Arrows. However, if the player also (or exclusively) has some Dwarven Arrows, then lower damage arrows will be converted to Dwarven Arrows.

Dwarven Arrow > Nordic Arrow

Rank 6: Elven Arrow, Bloodcursed Elven Arrow (DLC), Sunhallowed Elven Arrow (DLC)
Elven Arrows can always be converted to the Bloodcursed or Sunhallowed variants by NPCs from the DLCs if the player wants it. Thus, if the player has any arrow type from this rank as their highest damage arrow(s), lower damage arrows will always only be converted to Elven Arrows.

Elven Arrow > Bloodcursed Elven Arrow (NEVER CREATED) / Sunhallowed Elven Arrow (NEVER CREATED)

Rank 8: Ebony Arrow, Stalhrim Arrow (DLC)
If the player only has Stalhrim Arrows as their highest damage arrow, then lower damage arrows will be converted to Stalhrim Arrows. However, if the player also (or exclusively) has some Ebony Arrows, then lower damage arrows will be converted to Ebony Arrows.

Ebony Arrow > Stalhrim Arrow

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Please note that the actual damage output in the end is determined by more than just the base damage of the arrow you're using. I'm of course talking about the type of bow you're using to shoot the arrows as well as your achery skill and perks - these further modify the damage output.

Please note: apart from the instances specified in the special conversion rules, the script will never give you an arrow type that wasn't already present in your inventory. If you want to convert all your arrows over to a specific higher damage arrow, make sure you have at least 1 of that higher damage arrow type (and no other higher damage arrows) in your inventory before using conversion. Dropping arrows before using the conversion spell will make the conversion script ignore those arrows you dropped, and you can simply pick them back up from the ground after the conversion is completed.

Please note that the whole reason I'm giving the player the ability to determine for themselves when to initiate the conversion (by using the spell) is that turning lower damage arrows into high damage arrows will decrease the total amount of arrows you have. While it is cool to have, for example, 1 dragonbone arrows and 358 or so forsworn arrows turn into 101 dragonbone arrows, you do still go from having a total of 359 arrows before conversion to having a total of only 101 arrows after conversion. Sometimes you may still want to 'save up' lower or higher damage arrows.


Hope this answers any questions you may have, and I hope you have fun.


P.S. If you want to learn more about how I made this mod, I have put all the development and documentation files for this mod in a separate download on the download page. The documentation is not very well organized... I apologize for that. An exact step-by-step explanation of how to recreate this mod in the Creation Kit is provided in the text file 'SECOND ATTEMPT Script Documentation and Development' if you're interested.
Scripting for Skyrim and packing scripts into an archive is so annoying, honestly... I wouldn't recommend anyone use scripts in their mod. As someone with zero prior scripting background, I was grateful for the learning experience and glad to have been able to create this, but what a hassle it was.

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UPDATE - ALTERNATIVE VERSION

With some newfound inspiration, and since the earlier script was still fresh in my mind, I've attempted (and it seems, succeeded) to remake the conversion script so that it takes less code and would be more adaptable if necessary.
With this background information, I present an alternative version of the same mod in the downloads.

The end result is the same: it converts your lower damage arrows over to high damage arrows. 
And you can manipulate (e.g. dropping items you don't want to be included in the conversion) and control the spell in the same ways.
Behind the scenes, however, it works slightly differently. The script will detect the available arrows (same as the list of arrows mentioned above), and determine what the target arrow to convert to should be.
However, then it will add up all the damage values of all your lower damage arrows into one big sum, and then redistribute that sum into as best a fit of high-damage arrows as it can give you.
If there is some damage left over that isn't equal to any arrow, it will give you a 'free' extra arrow of the lowest damage type you had in your inventory.

E.g. you have 1 daedric arrow, 3 ebony arrows, 2 elven arrows, 2 dwarven arrows, 3 steel arrows and 3 iron arrows.
The Daedric arrow is the highest damage arrow and will be set as the conversion target that will be added to. The damage of all the other arrows is counted together into a sum: (3 * 20) + (2 * 16) + (2 * 14) + (3 * 10) + (3 * 8) = 194.
Out of this damage sum you get 8 daedric arrows and you'll have 2 damage left in the sum. No arrow does only 2 damage, so the script remembers your lowest damage arrow carried (iron arrows) and gives you an iron arrow for that remaining 2 damage (for a 'profit' of 6 damage, since iron arrows do 8 base damage each).

E.g. you have 1 daedric arrow, 6 dwarven arrows, 11 steel arrows and 88 iron arrows.
The Daedric arrow is the highest damage arrow and will be set as the conversion target that will be added to. The damage of all the other arrows is counted together into a sum: (6 * 14) + (11 * 10) + (3 * 10) + (88 * 8) = 84 + 110 + 704 = 898.
Out of this damage sum you get 37 daedric arrows and you'll have 10 damage left in the sum. Since a steel arrow does 10 damage, the script will also give you one steel arrow.

There is one quirk, though the script is technically working as intended.
When you are carrying 1 high damage arrow type + 1 lower damage arrow type (but not enough of it to convert to the high damage arrow type) and you activate the conversion...
...then it will remove the lower damage arrow(s) to put its/their damage into the sum, but then see that it can't convert this damage into the higher damage arrow, and since there is no other damage arrow types in between the lower and higher damage arrow, it will simply 'add' the lower damage arrow back to your inventory.
In this case it will display the notification that one or more arrows are added to your inventory, but really it's just adding back what it took away to perform the calculation, so you'll still have the same amount of arrows.

If you experience any issues with the original version of the mod (I don't see why you would since it normally works fine, but there could always be unforeseen circumstances) or if you're curious, you can give the alternative version a try.