  Background and objective: The stepped wedge cluster randomized trial is a
study design increasingly used for public health intervention evaluations. Most
previous literature focuses on power calculations for this particular type of
cluster randomized trials for continuous outcomes, along with an approximation
to this approach for binary outcomes. Although not accurate for binary
outcomes, it has been widely used. To improve the approximation for binary
outcomes, two new methods for stepped wedge designs (SWDs) of binary outcomes
have recently been published. However, these new methods have not been
implemented in publicly available software. The objective of this paper is to
present power calculation software for SWDs in various settings for both
continuous and binary outcomes.
  Methods: We have developed a SAS macro %swdpwr and an R package swdpwr for
power calculation in SWDs. Different scenarios including cross-sectional and
cohort designs, binary and continuous outcomes, marginal and conditional
models, three link functions, with and without time effects are accommodated in
this software.
  Results: swdpwr provides an efficient tool to support investigators in the
design and analysis of stepped wedge cluster randomized trails. swdpwr
addresses the implementation gap between newly proposed methodology and their
application to obtain more accurate power calculations in SWDs.
  Conclusions: This user-friendly software makes the new methods more
accessible and incorporates as many variations as currently available, which
were not supported in other related packages. swdpwr is implemented under two
platforms: SAS and R, satisfying the needs of investigators from various
backgrounds.
