How much does a sprite familiar's equipment count against its carrying capacity?

Question

Under Lifting and Carrying (PHB 176) it says:

Your carrying capacity is your Strength score multiplied by 15. This is the weight (in pounds) that you can carry... You can push, drag, or lift a weight in pounds up to twice your carrying capacity (or 30 times your Strength score).

and also specifies that a tiny creature can carry half as much.

A sprite familiar summoned through a warlock's Pact of the Chain feature has a strength score of 3 and so has a carrying capacity of 22.5 pounds, and a push, drag, lift limit of 45 pounds. The sprite stat block also specifies, however, that they wear leather armor and carry a longsword and shortbow.

By the rules in the PHB, these weigh 10 pounds, 3 pounds, and 2 pounds respectively, but considering they are smaller than those worn by a medium humanoid it one should assume that they do not weigh as much.

Is there any official guidance as to how much the sprite familiar's equipment counts against its carrying capacity?

Answer 1

5e offers no guidance on the subject of equipment weight for differently sized creatures

Unlike previous editions, nowhere in 5e's published rules is the question of equipment weight for larger or smaller creatures addressed. The DMG's section on designing new monsters briefly addresses weapons sized for larger creatures:

Big monsters typically wield oversized weapons that deal extra dice of damage on a hit. Double the weapon dice if the creature is Large, triple the weapon dice if it’s Huge, and quadruple the weapon dice if it’s Gargantuan.

But this is only about the damage the weapon deals. Weight is not addressed. As written, all equipment weighs the same no matter what size it is. This is obviously nonsense, but 5e's design has made a deliberate decision to elide these kind of concerns (in contrast to at least 3/3.5e, which covers the subject in a lot more detail). If the DM wants to get into this level of detail, they must decide for themselves what rulings to apply.

Personally, when I adjudicate item weight by creature size, I find that the easiest way to do it in the context of 5e's existing rules is simply to apply the same rules to equipment weight as apply to carrying capacity - which is to say, equipment for Tiny creatures weighs half what it normally does and equipment for creatures larger than Medium weighs double per step in size. It's not the most realistic ruling you could make, but it is at least consistent with the game's existing abstractions about weight and size.

Answer 2

Nothing official from any of the typical sources

Looking at the PHB, there is a section on "Variant Size Rules", but that is just do things fit, not adjusting for size.

The DMG is similar in its lack of detail.

This sorta fits with DnD 5e in general. It's trying to streamline and not get things bogged down with the minutia.

However

In fact the only place I could find mention of smaller and large equipment was the spell, Enlarge/Reduce:

Enlarge. The target's size doubles in all dimensions, and its weight is multiplied by eight. This growth increases its size by one category-- from Medium to Large, for example.
Reduce. The target's size is halved in all dimensions, and its weight is reduced to one-eighth of normal. This reduction decreases its size by one category--from Medium to Small, for example

So by those formulas, the Spite's equipment would be 1/64th the normal weight (1/8 for Small times 1/8 for Tiny). So by that the 10 pound armor would be a mere 2.5 ounces.