How long does an SAP S/4HANA migration take?
A typical SAP S/4HANA migration takes 15 to 20 months from start to go-live, according to SAPinsider's review of user-group benchmarks published in October 2026. ASUG's 2026 research, covering 194 member organisations, puts the average go-live at about 1.4 years. Your own timeline depends mainly on which migration path you choose and how much custom code and data you carry across.
Average timeline by migration path
| Migration path | What it means | Typical duration |
|---|---|---|
| Brownfield (system conversion) | Convert your existing ECC system, keeping configuration and history | 12 to 16 months |
| Selective data transition (bluefield) | New S/4HANA system with selected data and processes carried over | 12 to 18 months |
| Greenfield (new implementation) | Fresh S/4HANA system built around standard processes | 15 to 21 months |
Ranges combine SAP's indicative durations (brownfield 12 to 15 months, bluefield 12 to 18, greenfield 15 to 21 for a single wave) with ASUG's 2026 averages of 15.8 months for brownfield and 20.2 months for greenfield.
What the 2027 deadline means for your timeline
SAP ends mainstream maintenance for ECC 6.0 (enhancement packs 6 to 8) on 31 December 2027. That is about 14 months away. Optional extended maintenance runs to the end of 2030 for an extra fee.
With an average migration taking 15 to 20 months, most organisations starting now will not be live on S/4HANA before mainstream maintenance ends. That is manageable, but it needs a decision: budget for extended maintenance from January 2028, or narrow the scope to finish sooner.
The phases of a typical migration
- Assessment and business case. Agree the path, scope, budget and target date. Run SAP's readiness checks and size the custom code and data work.
- Preparation. Clean data, retire unused custom code, settle integrations and book the team.
- Build and convert. Configure or convert the system and rebuild what must change.
- Testing and rehearsals. Integration testing, user acceptance testing and at least one full cutover rehearsal.
- Cutover and go-live. Move to production, usually over a planned weekend or holiday window.
- Hypercare. A few weeks of close support while users settle and early issues are fixed.
What makes migrations take longer
ASUG's 2026 respondents who missed their go-live dates blamed:
- business changes during the project (55%)
- unexpected complexity (45%)
- scope creep (42%)
SAPinsider's 2025 research named the main complexity drivers as the data landscape (56%), replacing or re-engineering custom code (49%) and data harmonisation and cleansing (44%).
How to shorten your timeline
- Fix the scope early and protect it. Scope creep is one of the top three causes of delay.
- Start data cleansing first. Data is the most common complexity driver and can begin before the main project.
- Retire unused custom code before converting it.
- Rehearse the cutover at least once with production-sized data.
- Decide on extended maintenance early, so the deadline does not force a rushed go-live.
Frequently asked questions
How long does an S/4HANA migration take on average?
About 15 to 20 months. ASUG's 2026 research puts the average go-live at around 1.4 years.
Is brownfield faster than greenfield?
Usually. ASUG's 2026 data shows brownfield conversions averaging 15.8 months against 20.2 months for greenfield.
Can we finish before the end of 2027?
Only if you start soon with a tightly scoped project, typically a brownfield conversion. Most organisations starting in late 2026 should plan for extended maintenance as a fallback.
What happens if we miss the 2027 deadline?
You can buy optional extended maintenance for ECC until the end of 2030 at an extra cost.
Plan your S/4HANA move with Liditech
Liditech is a UK SAP consultancy that helps organisations plan and deliver S/4HANA migrations. A short assessment will give you a realistic timeline for your own system. See our S/4HANA consulting and SAP consultancy UK services, read what SAP consultancy costs in the UK, or contact us.