21 Grams is the final track on the 2017 album Everyone We Know by Thundamentals. The track features Hilltop Hoods and contains additional vocals from Mataya, even though she is not mentioned as a featuring artist.

The premise of the song is based on the myth that the soul of a human weighs about 21 grams. This myth originated from a study in 1907 by a doctor in Haverhill, Massachusetts that went by the name of Duncan MacDougall. This myth was later reinforced in the eponymous movie 21 Grams.