How does the Powerful Build racial feature affect carrying capacity?

Question

I came across the Powerful Build racial feature, which states:

You count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift.

I couldn't find any rules on how a creature's carrying capacity scales with its size. Can anyone clarify this?

Answer 1

In the vast majority of cases, you double their lift/push/drag/carrying capacity

Size and Strength. Larger creatures can bear more weight, whereas Tiny creatures can carry less. For each size category above Medium, double the creature's carrying capacity and the amount it can push, drag, or lift. For a Tiny creature, halve these weights.

—Lifting and Carrying, Player's Handbook, pg. 176

There's a few generalizations we can make based on this rule:

• There's no difference between Small and Medium creatures; they both use a multiplier of 1x.
• There are no [Officially Published] Racial Options in 5e that are 'Small'-sized, and have this feature

Therefore, we can generalize and say that any time a creature has this feature, you simply take their normal carrying/lifting/dragging/pushing capacity as determined for their size, and double it.

In the rare scenario where this feature gets applied to a 'Small'-sized creature, it would have no effect.

Answer 2

It's twice as much

Size and Strength. Larger creatures can bear more weight, whereas Tiny creatures can carry less. For each size category above Medium, double the creature's carrying capacity and the amount it can push, drag, or lift. For a Tiny creature, halve these weights.

(source)