Engineering Decision Tools
Two free, interactive tools we use in real engagements. Both run entirely in your browser, require no signup to start, and produce numbers you can defend in a budget meeting — not marketing estimates.
What are these free ERP tools?
In short: two interactive tools for CTOs and CFOs evaluating custom ERP. Model your licensing savings with the ERP ROI Calculator, or grade your current architecture in minutes with the Architecture Audit Grader. Both are free, run in your browser on Next.js, and need no signup.
ERP ROI Calculator
Model the total cost of ownership of your current SaaS licensing against a fixed-price custom build. Outputs two undiscounted 3-year totals and the savings between them, with every constant in the model printed beside it.
Calculate your ROIArchitecture Audit Grader
Answer a short assessment about your current stack — hosting, data model, integrations, security posture — and receive a graded scorecard highlighting the risks that matter most.
Grade your architecturePrefer a written deep-dive? Download the Systems Architecture Blueprint — the reference document behind both tools, listed alongside the technical manuals on the architecture resources index.
How each tool gets its numbers
ERPStack publishes these two engineering decision tools for teams comparing a custom ERP against SaaS. The ERP ROI Calculator sets the 3-year cost of a custom build on Next.js and PostgreSQL against per-seat SaaS licensing at $1,188 per user per year, across a 10 to 500 seat range. The Architecture Audit Grader scores your current stack out of 22 points across 5 questions on hosting, authentication, multi-tenant isolation and CI/CD cadence, and prints the arithmetic behind every number.
How does the ERP ROI Calculator model 3-year cost?
It builds two undiscounted 3-year totals from one input, seat count, and subtracts them. The SaaS side is a one-off implementation of $30,000 or $15,000 plus $800 per seat, whichever is larger, plus licences at $1,188 per user per year for 3 years, the published anchor for Oracle NetSuite and SAP mid-market seats. The custom side is a fixed build of $25,000 or $20,000 plus $500 per seat, whichever is larger, plus yearly hosting of $2,400 plus $24 per seat on AWS or Microsoft Azure, plus maintenance at 15% of the build. At 50 seats that is $233,200 against $76,050, a gap of $157,150.
How does the Architecture Audit Grader score a stack?
The grader asks 5 questions and adds their weights to a 22-point maximum, then reports the total as a percentage. Hosting model, authentication and RBAC, multi-tenant isolation and CI/CD frequency each score 1, 3 or 5 points. The fifth question, your biggest bottleneck, scores a flat 2 whichever answer you pick, because it routes the follow-up rather than grading you. 18 points and above reads as a flexible architecture, 12 to 17 as modernisation required, below 12 as a critical overhaul. The floor is 6 of 22, or 27%.
Which decision tool should you run first?
Run the Architecture Audit Grader first if you already own an ERP or CRM and want to know where it is fragile. It takes about 5 minutes and names the 2 gaps that stall most B2B Software procurement reviews and most SOC 2 or HIPAA readiness checks: authentication without SSO, and shared-tenant data without isolation. Run the ERP ROI Calculator first if the decision is buy against build and the blocker is budget rather than architecture. Most evaluations use both, then read the 24-component technology stack behind them and the published pricing before writing a business case.
Questions about these tools
Are these decision tools really free, and is a signup required?
Both tools are free and neither requires an account. The ERP ROI Calculator runs entirely in your browser and updates its 3-year figures the moment you move the seat slider. The Architecture Audit Grader shows your headline score out of 100 immediately after the fifth question; only the written gap analysis and the 48-hour architecture review ask for an email address. No card is requested by either of the tools at any point.
What discount rate do these decision tools assume?
None. The ERP ROI Calculator compares nominal, undiscounted cash totals over 3 years, so the figure it prints is a simple sum rather than a net present value. If your finance team discounts future spend, apply your own rate to the SaaS licence stream and to the custom hosting and maintenance stream separately. The licence stream is the larger and the later of the two, so discounting narrows the gap these decision tools report rather than widening it.
Do the ERP cost figures include software licence cost?
Yes, on the SaaS side, where the licence line is the single largest component: $1,188 per user per year, held flat for 3 years. The custom side carries no licence line at all, because an ERP built on PostgreSQL, Next.js, TypeScript and other open-source components has no per-seat fee. That structural difference is what these decision tools exist to size. Hosting on AWS or Microsoft Azure, maintenance and the one-off build replace the licence, and all 3 appear in the model.
Can I share a result from these tools with my CFO?
Yes. The ERP ROI Calculator writes your seat count into the page URL, so the copy-link button shares the exact estimate on screen rather than an empty form, and you can email the estimate to yourself from inside the tool. The Architecture Audit Grader keeps answers in browser local storage, so a half-finished assessment survives a closed tab. Both decision tools are built to be re-run in front of a CFO, not screenshotted once.
How accurate are the numbers these tools produce?
They are indicative models, not quotes. The SaaS licence anchor of $1,188 per user per year is deliberately conservative, because published Oracle NetSuite, SAP and Microsoft Dynamics 365 seat prices frequently run higher, so a real vendor quote usually widens the gap these tools report. The custom side uses the advertised floor of $25,000 and a 15% annual maintenance allowance. Scope, REST and GraphQL API integrations, and PostgreSQL data migration move both sides, which is why every figure links to a written estimate.