Compare monorepo and polyrepo build times. Calculate affected package builds vs per-repo builds with dependency overhead.
Choosing between a monorepo and polyrepo (multi-repo) architecture has significant implications for build times, CI/CD costs, and developer workflow. This calculator helps you compare build times under both strategies based on your project's characteristics.
In a monorepo, build systems like Turborepo, Nx, or Bazel can detect which packages are affected by a change and rebuild only those. The trade-off is longer initial setup and a larger repository. In a polyrepo, each repository has its own build pipeline, but changes to shared dependencies may trigger builds across multiple repos.
The optimal choice depends on your team size, number of packages, cross-package dependency frequency, and CI infrastructure. This calculator quantifies the build time difference to inform your decision.
Tracking this metric consistently enables technology teams to identify system performance trends and address potential issues before they impact end users or business operations. This measurement provides a critical foundation for capacity planning and performance budgeting, helping teams align infrastructure resources with application requirements and growth projections.
Monorepo vs polyrepo debates often lack data. This calculator provides concrete build time comparisons based on your project parameters, helping you make an evidence-based architecture decision. Precise quantification supports capacity planning and performance budgeting, ensuring infrastructure investments are right-sized for both current workloads and projected future growth. Data-driven tracking enables evidence-based infrastructure decisions, reducing the risk of over-provisioning costs or under-provisioning that leads to performance bottlenecks.
Monorepo Build = affected_packages × per_package_time + mono_overhead Polyrepo Build = Σ(per_repo_time + deps_overhead) for each triggered repo Difference = Polyrepo Build − Monorepo Build
Result: Mono: 13 min vs Poly: 15 min
Monorepo: 4 affected packages × 3 min + 1 min overhead = 13 min. Polyrepo: 3 repos × (3 + 2 min overhead) = 15 min. Monorepo is 2 minutes faster per build due to better affected-change detection.
Build time in both architectures depends on three factors: the work to be done, the overhead per build, and the degree of parallelization. Monorepos reduce redundant work through shared caches and affected-change detection. Polyrepos eliminate unrelated work by scoping each build to one repository.
Raw monorepo builds without optimization are slower than polyrepo builds because they attempt to build everything. The entire value proposition depends on intelligent build tools: Nx, Turborepo, Bazel, or Buck. Without these, monorepo build times grow linearly with package count.
Consider your team's cross-package change frequency, dependency sharing patterns, and CI infrastructure. If more than 30% of changes touch multiple packages, a monorepo with build optimization likely saves time. If packages are truly independent, polyrepo simplicity wins.
Monorepos are faster when: (1) many packages share dependencies, (2) changes frequently affect multiple packages, (3) you use build tools with affected-change detection, and (4) the alternative would trigger multiple polyrepo pipelines for shared changes. Comparing your results against established benchmarks provides valuable context for evaluating whether your figures fall within the expected range.
Polyrepos are faster when: (1) packages are independent with few shared dependencies, (2) changes rarely cross package boundaries, (3) teams work autonomously on separate services, and (4) individual repos are small and build quickly. Reviewing these factors periodically ensures your analysis stays current as conditions and requirements evolve over time.
Monorepo overhead includes change detection analysis, dependency graph computation, and cache management. With tools like Nx or Turborepo, this is typically 1–3 minutes. Remote caching can further reduce rebuilds by reusing previous outputs.
Each polyrepo build must resolve its dependencies independently: downloading packages, building shared libraries, and verifying versions. This adds 1–5 minutes per repo. Monorepos avoid this by using shared node_modules or build caches.
Yes. Many teams start with a polyrepo and gradually move related packages into a monorepo. Tools like Git subtree or repo-tool help merge histories. The reverse (splitting a monorepo) is harder but possible with git filter-repo.
Monorepo CI costs are typically lower because affected-change detection skips unmodified packages. Polyrepo CI can be wasteful when shared dependency updates trigger full rebuilds across all consuming repos.