Legacy ERP Parallel Run Cost Calculator
A parallel run feels safe, but it keeps two systems alive and doubles some work. This calculator prices that safety so you can choose the shortest run that still protects you.
Your numbers
Licences, hosting, support and admin that continue during the overlap.
Your results
Planning estimate. Replace defaults with your contract and payroll figures.
Extra cost vs parallel months
Sweeps Parallel run length from 1 to 12, holding your other inputs fixed.
Optional reconciliation automation
Ask how automated legacy to new comparisons could shorten your overlap.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the legacy cost that cannot be cancelled during the overlap, such as licence terms, hosting and support. Add double entry only if users truly key transactions twice. If you load data nightly instead, set the staff to zero and put the checking time into reconciliation hours.
The method
Incremental monthly cost equals legacy monthly cost plus extra labour. The new system cost is not incremental because it is spent regardless, though the tool shows total spend for reference. Total extra cost is incremental monthly cost times months, and the weekly figure shows what each slipped week costs.
Choosing a length
Most teams need at least one full period close, often two. Parallel running past a clean quarter-end rarely adds assurance. Use the chart to see how the cost climbs per month and set an exit criterion such as three consecutive reconciled closes, rather than a calendar date alone.
- Define exit criteria first
- Cancel what you can early
- Negotiate short legacy extensions
- Automate reconciliation
Frequently Asked Questions
Is a parallel run mandatory?
No. Some companies cut over after rehearsals and keep the legacy system read-only. A parallel run suits high-risk financial processes, but it costs time and attention that rehearsals can often replace.
Why exclude the new system cost?
Because you will pay it whether or not you run in parallel. Only costs that exist because of the overlap belong in the incremental figure.
What does reconciliation cover?
Comparing trial balance, open AR and AP, inventory valuation and key reports between systems, and investigating differences.
How long should the legacy system stay readable?
Often for audit and tax retention periods, typically several years. See the data growth and archive calculator for storage planning.
Netray can build automated reconciliation between legacy and new ERP data so the run can be shorter. The calculator is independent of that.
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More ERP Migration & Selection tools
See all- ERP TCO Comparison Calculator (5-Year)
- ERP Migration Risk Assessment
- Data Migration Effort Calculator
- ERP Selection Scorecard for Manufacturers
- ERP Go-Live Readiness Checklist
- ERP Change Management Readiness Assessment
- ERP Integration Complexity Calculator
- Cloud vs On-Premise ERP Cost Calculator
- ERP Upgrade vs Replace Assessment
Keep exploring
Free tools
- JD Edwards World Parallel Run Cost CalculatorAdd up the cost of running the old and new systems together, including reconciliation and slippage, and see the true incremental cost of the overlap.
- Legacy ERP On-Prem Run Cost CalculatorAdds servers, SQL licences, admin staff, disaster recovery and vendor maintenance into one annual run cost with a multi-year inflation view.
- Legacy ERP Retirement Cost and Payback CalculatorCompare the annual run cost of a legacy IBM i ERP with a replacement, include migration and parallel run costs, and see payback and net savings.
ERP fixes and how-tos
- Baan IV to Infor LN migration checklistPlan a Baan IV to Infor LN move as a re-implementation, not a patch: inventory customizations, convert data, rebuild logic, and run a real parallel test.
- Private AI Layer for Baan On-Prem: Reference ArchitectureReference architecture to add a private AI assistant to Baan on-prem: data access paths, retrieval, permissions, sizing and rollout, no cloud needed.
- Adding AI to a Legacy ERP Without Replacing ItYes, most legacy ERPs can get a grounded AI layer without a rip-and-replace. What data access you need, what AI can and cannot fix, and how to start.
Guides
- ERP Parallel Testing MethodologyExecute ERP parallel testing with structured reconciliation methods. Compare legacy and new system outputs to validate data accuracy before go-live.
- AI-Powered Legacy ERP ModernizationModernize legacy ERP systems with AI. Gradual transformation from BPCS, MAPICS, BAAN, and other legacy systems to modern Infor cloud ERP.
- ERP Legacy Data Archival StrategyPlan your legacy ERP data archival strategy for compliance and cost efficiency. Address retention requirements, access needs, and decommissioning timelines.