DMAIC|4 min read
SIPOC diagram: when to use it and how to build one
SIPOC — Suppliers, Inputs, Process, Outputs, Customers — is a scoping tool, not a process map. It lives in Define. It takes 30 minutes. It prevents most of the scope arguments that derail DMAIC projects in Measure.
The 5 columns
| Column | What goes in it | Question to ask |
|---|---|---|
| Suppliers | Who provides inputs? | Who sends us what we need? |
| Inputs | What do suppliers send? | What do we need to start? |
| Process | 3–7 high-level steps | What's the rough flow? |
| Outputs | What leaves the process? | What do we produce? |
| Customers | Who receives outputs? | Who cares about the output? |
Build order
Fill it out of order: start with Customers and Outputs (the end), then Suppliers and Inputs (the start), then 3-7 Process steps in the middle. Starting with the process makes it too easy to get stuck in detail.
Common mistakes
- Too many process steps — keep it to 3-7. If you need more, do a process map, not a SIPOC.
- Listing equipment as Inputs — inputs are what flows through the process, not what the process runs on.
- Forgetting internal customers — the next department is a customer too.
When SIPOC is the wrong tool
SIPOC is for scoping, not analysis. It doesn't show wait time, defect rate, or decisions. Once scoping is done, move to a process map or VSM for the detailed work.