Rebuild vs Refactor calculator
Sitting on aging software and torn between a clean rebuild and a careful refactor? Cost is only half the story, tech debt and how much of the current system is worth keeping decide the rest. Set your inputs to see the cheaper path and whether it's actually the safer one.
How it works
The rebuild vs refactor software decision is rarely about which number is smaller. Refactoring reworks the code you already have, keeping the data model, business logic and hard-won institutional knowledge, while a rebuild starts from a blank page. This tool estimates a refactor as a fraction of a full rebuild, scaled by how bad the tech debt is and how much of the current system is genuinely worth keeping.
Two forces drive it. Tech debt sets the multiplier: clean code refactors cheaply, but severe, brittle code costs far more to untangle than to replace. Salvage valuethe share of features, schema and logic you can carry forward, pulls the refactor cost down. The catch: when debt is severe, almost nothing is worth keeping, or you are investing in a long-term platform on a weak base, a refactor quietly becomes a rewrite in disguise, so the tool recommends a clean rebuild even when the refactor looks cheaper on paper.
Refactor cost = rebuild cost × debt factor × (1 − keep% ÷ 300)
Recommend rebuild when debt is severe, little is worth keeping, or you are building long-term on a marginal codebase
Remember that a rebuild is riskier and slower than its estimate implies, feature-parity gaps, scope creep and running two systems at once all cost real time. To pressure-test the rebuild figure, run your scope through the software development cost calculator, or browse the rest of our free tools.