How to Estimate Man-Days in ERP Projects?
Man-day estimation is not only about budget; it is about scope clarity and delivery credibility. Under-selling effort breaks the plan; over-selling erodes trust. This guide summarizes a three-level approach, a step-by-step method, and typical Canias ERP multipliers. Educational only.
Table of contents
Three levels of estimate
Rough order-of-magnitude, scope-based (work breakdown), and plan-based (detailed tasks). Depth increases as the project matures.
- Rough estimate: benchmarks and similar projects; often ±50% band.
- Scope-based: process/area breakdown, effort class; risk separate.
- Plan-based: task list, P50/P80 split; include PMO/coordination effort.
Step-by-step method
Break scope into parts; assign an effort class per part. Use benchmarks; show risk separately. Do not forget PMO and coordination. Separate P50 (median) from P80 (safer).
- Split scope into work packages.
- Effort class (small/medium/large) with benchmark hours.
- Apply multipliers for integration, data migration, TROIA needs.
- Add a complexity factor for multi-site / multi-company setups.
- Show risk and uncertainty as its own line.
Typical multipliers in Canias ERP programs
Integration, data migration, TROIA development, and multi-company structures increase effort. Evaluate them explicitly.
- Integration: test and adaptation per critical interface.
- Data migration: source quality and volume.
- TROIA needs: customization volume.
- Multi-site / company: data model and authorization complexity.
Common mistakes
Estimating before scope is clear; omitting PMO/coordination; hiding risk in a single number; skipping benchmarks.
- Giving one number before scope is settled.
- Ignoring coordination and meeting cost.
- Budgeting on P50 but planning without P80.
- Not using data from similar projects.
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- What do P50 and P80 mean?
- P50 is the median scenario (50% probability of not exceeding). P80 is a safer scenario (80%). It is common to budget around P50 and plan buffers toward P80.
- Why list PMO effort separately?
- Meetings, reporting, coordination, and decision tracking are load on top of direct delivery. If omitted, estimates stay artificially low.
- Where do Canias projects most often slip?
- Data migration, integration, and customization (TROIA) durations are often underestimated.
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