QM Bench

SIPOC diagram: theory, step-by-step guide and example

How to scope a process with Suppliers, Inputs, Process, Outputs and Customers before an improvement project, in which order to fill it and a worked example from shaft production.

Ľubomír Blažek
Automotive quality manager · updated 2026-10-25

Try it while you read

Open the free SIPOC Diagram tool and click Load sample: it reproduces the case study below.

Open the tool

Theory: agree on the scope first

Many improvement projects fail because the team disagrees on what is inside the project. SIPOC, a standard tool in the Define phase of Six Sigma (DMAIC), puts the process on one page: who supplies what, what happens in a few high-level steps, what comes out and who receives it.

It also makes the customer visible: every output has a receiver with requirements, which later become the critical-to-quality characteristics to measure.

Key point

A SIPOC is done in 30 to 60 minutes with the team. If it takes longer, the process boundaries are not clear yet, which is exactly what the exercise is meant to reveal.

Step by step

  1. Name the process and its start and end in the report header.
  2. Process: 4 to 7 steps, one per line, verb + noun.
  3. Outputs and Customers: internal and external.
  4. Inputs and Suppliers: material, information, resources.
  5. Download the diagram as PNG, SVG or PDF for the project charter.

Example: shaft production

The Load sample SIPOC scopes a scrap project:

  • Suppliers: steel supplier, tool supplier, planning, metrology lab.
  • Inputs: bar stock C45, inserts and holders, work order and drawing, calibrated gauges.
  • Process: saw bar to length → turn on CNC → heat treat → grind bearing seats → inspect and pack.
  • Outputs: finished shafts, inspection records, SPC data, shipping labels.
  • Customers: gearbox assembly, logistics, quality department.

The team agrees that heat treatment is outside the project (separate supplier contract), which keeps the scope manageable. Next steps are a Pareto of scrap and an A3.

Common mistakes

  • Too many process steps: the SIPOC turns into a flow chart.
  • Forgetting internal customers and information outputs.
  • Doing it alone instead of with the process owners.

Frequently asked questions

Why fill it from the middle?

Starting with the process steps and then going to outputs and customers keeps the focus on what the process delivers. Inputs and suppliers follow from what the steps need.

How detailed should the process steps be?

High level: 4 to 7 steps. The SIPOC is for scoping, not for a detailed flow chart or value stream map.