Six Sigma Tools: The Complete List by DMAIC Phase

If you’ve studied for a Six Sigma exam, you’ve met dozens of Six Sigma tools: FMEA, Pareto charts, Control Plans, Fishbone diagrams. Each one is taught on its own page, with its own formula or procedure. What’s harder to find is one place that shows all the major tools at once. Better still, organized by where they get used in a project. That’s what this page is for.

Six Sigma tools are the specific techniques, templates, and statistical methods a project team uses to move through DMAIC (Define, Measure, Analyze, Improve, Control). DMAIC is the problem-solving framework at the center of every Six Sigma project. Some tools are purely qualitative. For example, a Fishbone diagram is just a structured conversation. Others, like a hypothesis test, are rigorously statistical. Most projects use a mix of both. Below, the major Six Sigma tools are grouped by DMAIC phase. After that come the cross-cutting Lean tools and the classic “7 tools” sets that appear on every certification exam.

Two things trip people up when they first look at a list like this. First, not every tool belongs to exactly one phase. For instance, Process Mapping often gets redone in Measure and again in Improve. Similarly, Control Charts can baseline a process in Measure and sustain it in Control. So the groupings below show where each tool is most commonly introduced. They are not a hard rule. Second, more tools doesn’t mean a better project. The best Black Belts pick the smallest set of tools that answers the question in front of them. They don’t force every tool into one project to prove they know it.

Define Phase Tools

The Define phase establishes what problem you’re actually solving, for whom, and why it matters. These tools get the team, the sponsor, and the customer agreeing on one problem. That happens before anyone collects data. Rushing this phase is a common reason projects stall. A team that disagrees on scope in week one will usually discover it in week six, after a lot of wasted analysis.

• Project Charter: the foundational document for the project. It states the business case, problem, goal, scope, and team roles. It’s the first thing a Belt builds. It stays the reference point for the whole project.
• SIPOC: a high-level process map showing Suppliers, Inputs, Process, Outputs, and Customers. It’s the fastest way to establish process boundaries before diving into detailed mapping.
• Voice of Customer (VOC): the structured process of capturing what customers need. Teams use surveys, interviews, complaints, or observation, then translate the needs into measurable requirements.
• Critical to Quality Tree (CTQ): translates a broad customer need into specific, measurable quality requirements a process must hit.
• Critical to Cost (CTC): the same translation exercise as a CTQ tree, focused specifically on the cost drivers a customer or business cares about.
• Critical to Safety (CTS): identifies the safety requirements a process or product must meet. It’s often used alongside CTQ in regulated industries.
• Stakeholder Analysis: identifies everyone who influences or is affected by the project. It also maps how to manage and communicate with each one.
• Communications Plan: formalizes who needs what information, how often, and through which channel, for the life of the project.

Measure Phase Tools

The Measure phase establishes a factual baseline for how the process performs today. It comes before anyone proposes a fix. This is also where a surprising amount of project time gets spent, not on fancy analysis, but on making sure the data being collected is trustworthy in the first place. A Measurement Systems Analysis that gets skipped here tends to quietly undermine every statistical conclusion drawn later.

• Data Collection Plan: specifies what data will be collected, how, by whom, and how often. Writing it first saves the team from reworking a messy dataset later.
• Check Sheet: a simple form for tallying data by hand where it occurs. It’s often the first data-collection tool a team builds.
• Process Mapping: a visual, step-by-step diagram of how work actually flows through a process today, as opposed to how it’s assumed to flow.
• Histogram: a bar chart showing how often different value ranges occur. It’s the fastest way to see a process’s shape, center, and spread.
• Pareto Chart: a bar chart ranking causes by frequency or impact. It’s built on the 80/20 rule: a few causes usually drive most of the problem.
• Box Plots: a compact summary of a dataset’s median, quartiles, and outliers. It’s especially useful for comparing several groups side by side.
• Measurement Systems Analysis (MSA): verifies that the measurement system itself can be trusted. That covers the gauge, the method, and the people measuring.
• Gage R&R: a specific MSA study. It splits measurement variation into the gauge itself (repeatability) and the people using it (reproducibility).
• Control Charts: time-ordered plots that separate normal variation from special-cause variation. The special causes are the ones worth investigating. See also the specific chart types: I-MR, XmR, and EWMA.
• Process Capability (Cp & Cpk): measures whether the process, as it runs today, can consistently meet customer specification limits.

Analyze Phase Tools

The Analyze phase moves the team from “here’s the baseline” to “here’s what’s causing the problem.” It uses both structured brainstorming and statistical testing. The discipline here is resisting the urge to jump to a favorite fix. The qualitative tools (Fishbone, 5 Whys) list the suspected causes. Then the statistical tools (Hypothesis Testing, Regression) confirm or eliminate each suspect with evidence.

• Cause and Effect Diagram (Fishbone/Ishikawa): a structured brainstorming tool that sorts possible causes into categories, commonly the 6Ms. The categories branch off a central “spine” toward the effect.
• 5 Whys: a simple root-cause technique of repeatedly asking “why” to peel back symptoms and reach the underlying cause of a problem.
• Root Cause Analysis: the umbrella discipline of finding the true cause of a problem instead of treating symptoms. It usually combines several tools on this page.
• Failure Mode Effects Analysis (FMEA): a systematic risk-assessment tool. It scores failure modes by severity, occurrence, and detection to show which risks need action first.
• Hypothesis Testing: the statistical framework for deciding whether a difference in your data is real. The alternative is that chance alone explains it.
• Regression Analysis: a statistical method for modeling how inputs relate to an output. It measures how much the output moves when an input changes.
• Scatter Diagrams: a quick plot of two variables against each other. It’s often the first check for a relationship, before a formal regression.
• Multi-Vari Study: a structured way to observe a process without changing it. It narrows down which family of variation drives the problem: within-unit, between-unit, or over-time.
• Cause and Effect Matrix (X-Y Diagram): a scoring matrix for input variables (X’s). It ranks each one by how strongly it affects the outputs (Y’s) the customer cares about.
• TRIZ: a problem-solving method built from patterns in thousands of patents. It helps find creative solutions that resolve a contradiction instead of compromising.

Improve Phase Tools

The Improve phase is where the team generates, tests, and selects the actual solution, then pilots it before a full rollout. This phase uses two families of tools. Creativity tools help a team generate and organize solutions (Affinity Diagram, Tree Diagram). Verification tools confirm a solution works at small scale first (DOE, a pilot run).

• Design of Experiments (DOE): a rigorous way to test several factors at once. It shows which factors, and which combinations, drive the outcome.
• Value Stream Mapping: maps the full flow of material and information needed to deliver a product or service. Its purpose is to separate value-added steps from waste.
• Kaizen: a focused, rapid-improvement event aimed at removing one source of waste quickly. The word also names a broader philosophy of small, continuous improvements.
• Poka-Yoke (Error-Proofing): designs a process so a specific mistake becomes impossible or is caught immediately. It replaces inspection after the fact.
• 5S: a workplace organization method (Sort, Set in Order, Shine, Standardize, Sustain). It removes clutter and variation from the workspace itself.
• SMED (Quick Changeovers): a method for radically reducing the time it takes to switch a process or machine from running one product to running another.
• Pugh Analysis: a structured decision matrix for comparing several candidate solutions against a baseline, across multiple weighted criteria.
• Tree Diagram: breaks a broad goal down into progressively more specific tasks and sub-tasks needed to achieve it.
• Affinity Diagram: organizes many separate ideas into natural groups. It helps make sense of brainstorming on an unfamiliar problem.
• Interrelationship Digraph: maps cause-and-effect links between connected issues. It shows which issues are root drivers and which are downstream effects.
• Prioritization Matrix: ranks competing options against shared, weighted criteria. That focuses effort where it has the most impact.
• House of Quality (QFD): translates customer requirements into design characteristics. That way, what gets built maps back to what the customer asked for.

Control Phase Tools

The Control phase locks in the gains from Improve. Otherwise the process quietly drifts back once the team moves on. This phase is the most likely to be shortchanged under deadline pressure. That’s backwards. A fix with no monitoring plan is temporary, no matter how good the solution was.

• Control Plan: documents how the new process will be monitored. It names who owns each check, how often it runs, and what to do if a measurement goes out of range.
• Statistical Process Control (SPC): the ongoing use of control charts on a live process. It separates normal variation from a real shift that needs action.
• Standard Work: documents the current best way to perform a task. As a result, the improvement is followed consistently instead of left to habit.
• Response Plan: a control-phase tool named in the IASSC BOK. It’s a predefined plan for the moment a metric goes out of control, so nobody improvises under pressure.

Lean Tools (Used Across Every Phase)

Lean tools focus on removing waste and improving flow. They show up throughout a Lean Six Sigma project, not in one DMAIC phase. The DMAIC tools above are mostly diagnostic: they find what’s wrong and prove it. Lean tools, by contrast, are prescriptive. They remove a known type of waste once you’ve found it. That’s why Lean and DMAIC tools often pair up. For example, a Spaghetti Diagram (Lean) reveals wasted motion, and a revised Process Map (DMAIC) documents the fix.

• Classic Wastes (the 8 Wastes): the standard Lean checklist of waste types, often remembered as TIMWOODS. It trains your eye to spot non-value-added work.
• Kanban: a visual signal that pulls work through a process based on real downstream demand. It replaces pushing work from a forecast.
• Spaghetti Diagram: traces the physical path a person, part, or document takes through a workspace. It usually exposes an absurd amount of travel at a glance.
• 8D Method: an 8-step, team-based problem-solving method common in automotive and manufacturing. It runs from containing a problem to preventing it from coming back.

The Tools You’ll Actually Use Most Often

Every one of these Six Sigma tools earns its place in some BOK. In practice, though, a handful carry most real projects. Say you had time to master five tools before a real project, not an exam. Practitioners consistently name the same short list:

• Process Mapping, because almost nothing else is possible until the team agrees on how the process really works today.
• Cause and Effect (Fishbone) Diagram, because it’s the cheapest way to get a team’s knowledge onto one page. It comes before any statistics.
• Pareto Chart, because it answers the single most useful question on any project: out of everything that could be wrong, what’s actually worth our time?
• Control Charts, because they follow a process from Measure through Control. They baseline the process and later prove the fix held.
• FMEA, because it forces a team to think about failure before it happens, rather than reacting to it after a customer finds it first.

That’s no reason to skip the rest. A true root-cause question will need Hypothesis Testing or DOE. Similarly, a project with a safety or planning angle will need the qualitative Improve tools. But if the full list feels overwhelming, get comfortable with those five first.

The Classic “7 Tools” Sets

Two groupings of Six Sigma tools show up by name on nearly every certification exam. Know them as named sets, not just as single tools.

• The 7 Basic Quality Tools: the original quality-control toolkit. It includes the Cause and Effect Diagram, Check Sheet, Control Chart, Histogram, Pareto Chart, Scatter Diagram, and Process Mapping (sometimes taught as a Flowchart). Every one of these has its own dedicated page above.
• The 7 Management and Planning Tools: a newer, more qualitative set for planning complex, non-numerical problems. It includes the Affinity Diagram, Interrelationship Digraph, Tree Diagram, Prioritization Matrix, Matrix Diagram, PDPC, and Activity Network Diagram.

Choosing the Right Tool

With this many Six Sigma tools, the real skill isn’t memorizing them all. It’s knowing which tool fits the question you’re asking. A few quick rules of thumb:

• If you need to agree on what the problem is, reach for Define phase tools (Project Charter, SIPOC, VOC, CTQ).
• If you need to know how big the problem is right now, reach for Measure phase tools (Process Mapping, Histogram, Control Charts, Process Capability).
• If you need to know why it’s happening, reach for Analyze phase tools (Fishbone, 5 Whys, Hypothesis Testing, Regression).
• If you need to test or implement a fix, reach for Improve phase tools (DOE, Kaizen, Poka-Yoke, Pugh Analysis).
• If you need to make sure the fix sticks, reach for Control phase tools (Control Plan, SPC, Standard Work).

Here’s how that plays out on an actual project. Say a Green Belt is asked to fix a call center’s slow response times. The project doesn’t start with a statistical test. Instead, it starts with a Project Charter to pin down the scope: which queue, which customers, what counts as “too slow.” It also needs a SIPOC to confirm where the process actually begins and ends.

Only once that’s settled does the team build a Process Map and start pulling Control Chart data to see what “normal” currently looks like. If the data shows real, unexplained variation, a Fishbone Diagram and a few rounds of 5 Whys narrow the list of suspects, and Hypothesis Testing confirms which suspected cause is statistically real versus which one just looked convincing in a meeting. Only then does the team move to Kaizen or a small DOE to test a fix, and finally a Control Plan to make sure response times don’t quietly drift back up three months later. Notice that the team never needed all 40-plus tools. They needed about seven, in a specific order, each answering one question.

Most real projects don’t use every Six Sigma tool on this page. They use the handful that answer the question in front of the team. If you’re studying for a certification exam, your belt’s body of knowledge tells you which tools you must know in depth and which you only need to recognize. For example, a Yellow Belt should recognize most tools here. A Black Belt, by contrast, should run the statistical ones (hypothesis testing, regression, DOE) without guidance.

Frequently Asked Questions

How many Six Sigma tools are there?

There’s no single official count. Different bodies of knowledge (ASQ, IASSC, Villanova) name somewhat different lists. Also, some tools overlap with general project management or Lean. This page covers about 40 of the most commonly taught Six Sigma tools, grouped by DMAIC phase. That covers most of what any certification body will test.

Which Six Sigma tools does a Black Belt need to know that a Green Belt doesn’t?

The split is less about which tools a Black Belt knows and more about depth. Both belts learn most of the Six Sigma tools on this page. However, a Black Belt runs the advanced statistical tools independently: multi-factor DOE, advanced regression and ANOVA, and less common hypothesis tests. A Green Belt runs and interprets the basics, with support.

Are Lean tools and Six Sigma tools the same thing?

No, though they’re used together so often that the line blurs in practice. Six Sigma tools mostly reduce variation and defects through data. Lean tools, on the other hand, reduce waste and improve flow, often without statistics. A combined Lean Six Sigma project draws from both. Which one leads depends on whether the problem is variation or flow and waste.