What are the dimensions of a box that can contain 20 arrows?

Question

I am playing a level 13 Fighter with the Sharpshooter martial archetype (from Unearthed Arcana: Fighter). I took the Sharpshooter feat as well, of course, and the Archery fighting style. I shoot between 3 and 6 arrows per round (using Action Surge and Extra Attack), so I need a lot of arrows to keep me going through combat.

A Bag of Holding seems to be best option for holding the arrows I will need; since I read this thread, I plan on using a box to hold the bundles - presumably 1 box per bundle to keep things organized.

What dimensions would such a box need to be able to hold 20 arrows?

I am specifically asking for the dimensions of a box that can hold 20 arrows because that determines how many boxes I can put in a bag of holding, which will equal how many arrows I can safely put in a bag of holding.

Answer 1

RAW:

Quiver holds 20 arrows and weighs 1 pound, and 20 arrows weigh 1 pound. (PHB p.152-153)

Bag of Holding:

The bag can hold up to 500 pounds, not exceeding a volume of 64 cubic feet. (DMG p.153)

By weight, this gives us an absolute maximum of 250 loaded quivers.

Dimensions are not given by RAW:

But if we look at typical arrows. They are 30-32 inches in length with fletchings that are about 3/8 of an inch tall. If we allow a little extra space for manipulating the arrows, we get a case/quiver that is 2x10x36 inches; or 3/7 of a cubic foot.

By volume with the assumed dimensions, we can fit 149 loaded quivers in the Bag of Holding

Note: There are many different styles of quivers. It is possible to have a capped quiver that protects the arrows and allows access by simply removing the cap.

Answer 2

You don't need a box to protect the bag

The bag of holding is a magic item -- the inside is not actually a bag that could be pierced by the arrows you put in, it is an extradimentional space. It does not say so itself, but the handy haversack does:

Placing the haversack inside an extradimensional space created by a bag of holding, [...]

That means there is no risk of the arrows piercing your bag from the inside (well, check with your DM to be sure, because in earlier editions, you could damage the bag from inside, and they may be used to that. But in 5e everyone I know is dropping swords and spears and other sharp objects into the bag without any concern about the bag potentially being destroyed by being punctured.) You can just wrap/tie the bundles with string, and save yourself the extra space and weight of quivers.

Capacity

The bag can hold up to 500 pounds, not exceeding a volume of 64 cubic feet.

You only have to be careful that you do not overload it, weight wise, or it will rupture and be destroyed. As 20 arrows weigh 1 pound, that would mean you could put in 20 x 500 or 10,000 arrows by weight.

Arrows can vary a lot in length and head, but the game is not that detailed about it. Medieval arrows used to be about 21 inches long, and maybe half an inch in shaft thickness, so giving some space for the heads, you could pack them into a package of about 3 x 3 x 21 inches, or about 0.1 cubic feet. With 64 cubic feet available, you could pack in about 640 packs, or 20 x 640 arrows, which means the weight willl limit you before the space. That's good too because it is way easier to track during play. Nobody I know takes the effort to calculate the space.

Action economy

It is not a great idea to get the arrows out during a fight, because:

Retrieving an item from the bag requires an action.

And you don't want to spend your action in mid-combat on that. So it would work better for you to just stash arrows, and re-stock your normal quiver with a new bundle that you put in after removing the strings after the fight - maybe get a second normal quiver, too. Even when firing 3-6 arrows per round, a normal fight just takes 3-4 rounds so on average you will only need 16 arrows, and in the worst case, maybe 24 so a double quiver should be plenty, and it will cost you no extra actions.