Power counting in the soft-collinear effective theory

We describe in some detail the derivation of a power counting formula for the soft-collinear effective theory (SCET). This formula constrains which operators are required to correctly describe the infrared at any order in the ${\Lambda }_{\mathrm{QCD}}/Q$ expansion $(\lambda$ expansion). The result assigns a unique $\lambda$ dimension to SCET graphs solely from vertices, is gauge independent, and can be applied independent of the process. For processes with an OPE the $\lambda$ dimension has a correspondence with a dynamical twist.