Monte Carlo and Bayesian Stop-Signal Reaction Time Estimation R package SSRTcalc version 2.1.1 Estimates stop-signal reaction time (SSRT) in the stop-signal task using the integration and mean methods described by Verbruggen and colleagues (2019) <doi:10.7554/eLife.46323>. In addition to point estimates, the package provides Monte Carlo tools (nonparametric bootstrap confidence intervals, parametric ex-Gaussian simulation, minimum-trial-count and power analysis, and sensitivity analysis under violations of the horse-race assumptions) and Bayesian estimation via 'Stan', including single-subject and hierarchical ex-Gaussian horse-race models with an optional trigger-failure parameter following Matzke and colleagues (2013) <doi:10.1037/a0030543>, posterior inhibition functions, and posterior predictive checks. The Bayesian layer works with either the 'cmdstanr' or 'rstan' backend. Software Depends: R (>= 4.0.0) Imports: stats, graphics, grDevices Suggests: MASS, cmdstanr (>= 0.5.0), rstan (>= 2.26.0), posterior, bayesplot, loo, parallel, testthat (>= 3.0.0) Anton Leontyev <antonleontyev@missouristate.edu> Comprehensive R Archive Network (CRAN) Anton Leontyev [aut, cre] (ORCID: <https://orcid.org/0000-0001-8880-6161>) GPL-3 2026-07-06 application/tgz https://CRAN.R-project.org/package=SSRTcalc doi:10.32614/CRAN.package.SSRTcalc