How Long Does a Software Project Really Take?

Why Estimates Fail

Unclear Special Cases. It is not the main function that takes time, but the exceptions. "What happens in the case of a partial cancellation after invoicing?" is the type of question that can cost weeks in implementation if it is missing from the concept.

Decision Speed. If every query waits a week for an answer, the duration doubles – regardless of technology and team size. This is the most underestimated factor.

External Systems. Every integration depends on the schedule of a third party. Waiting for a test access to an ERP interface often takes longer than the implementation itself.

Effort is Not Calendar Time

Ten person-days do not equal two weeks. A working year in Germany has about 250 to 260 working days. After deducting vacation – the legal minimum vacation is 24 working days for a six-day week (§ 3 BUrlG), with 25 to 30 days being common for a five-day week – and the eleven public holidays in North Rhine-Westphalia and sick days, about 210 to 220 available days per person per year remain.

Additionally: No one works 100 percent on a project. Anyone planning with full availability is planning a fiction.

The Four Items Missing from Every Schedule

1. Data Cleansing. The effort rarely lies in the import, but almost always in the legacy data: duplicates, missing mandatory fields, historically grown codes.
2. Testing by the Specialist Department. People who truly know the process have daily business. Their testing time must be planned and freed up.
3. Training and Documentation.
4. Post-Launch Adjustments. The first two to four weeks in live operation bring insights that no test provides.

These four items constitute a significant part of the overall effort and are completely missing from most plans.

The Only Deadline Recognized by Law

Not the go-live counts legally, but the acceptance (§ 640 BGB). It is the pivotal point:

Important is § 640 Abs. 2 BGB: If the contractor sets a reasonable deadline for acceptance after completion and the client does not refuse it by stating at least one defect, the work is considered accepted. Silence thus ends the uncertainty – to the detriment of the one who remains silent.

How long defect claims for software expire is disputed: The two-year period of § 634a Abs. 1 Nr. 1 BGB and the regular limitation period according to Nr. 3 are relevant. That is precisely why the deadline must be explicitly included in the contract.

What Realistic Planning Looks Like

The number of screen masks is deliberately not included in this table. Twenty similar masks are built faster than five with their own logic each.

What You Can Actually Accelerate

• A contact person with decision-making authority, not a committee
• Early designated test users from daily business, with freed-up time
• Obtain access and interface documentation before the project begins
• Limit the scope and divide it into sections that can be used individually

All of this costs no money and has a greater impact than any technical decision.

The Values of This House

First usable version: upon request. Complete project: upon request.