If you’ve spent any time studying for a Six Sigma exam, you’ve run into dozens of individual tools, FMEA, Pareto charts, Control Plans, Fishbone diagrams, each taught on its own page, in its own module, with its own formula or procedure. What’s harder to find is a single place that steps back and shows you all of the major Six Sigma tools at once, organized by where they actually 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), the structured problem-solving framework at the center of every Six Sigma project. Some tools are purely qualitative (a Fishbone diagram is just a structured conversation), others are rigorously statistical (a hypothesis test or a designed experiment), and most projects end up using a mix of both. Below, you’ll find the major Six Sigma tools grouped by DMAIC phase, plus the cross-cutting Lean tools and the classic “7 tools” sets that show up across every certification body’s exam.

Two things trip people up when they first look at a list like this. First, not every tool belongs to exactly one phase, Process Mapping, for instance, often gets redone at both Measure and Improve, and Control Charts can appear as early as Measure (to baseline a process) and again at Control (to sustain it). The phase groupings below reflect where each tool is most commonly introduced, not a hard rule. Second, more tools doesn’t mean a better project. The best Black Belts are the ones who pick the smallest set of tools that actually answers the question in front of them, not the ones who force every tool on the list into a single project just 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 everyone, the team, the sponsor, and the customer, agreeing on the same problem before anyone starts collecting data. Skipping or rushing this phase is one of the most common reasons projects stall later: a team that disagrees on scope in week one will usually surface that disagreement in week six, after a lot of wasted analysis.

• Project Charter: the foundational document that states the business case, problem statement, goal statement, scope, and team roles for the project. It’s the first thing a Black Belt or Green Belt builds and the reference point for the entire 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 actually need, through surveys, interviews, complaints, or direct observation, and translating that into specific, 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 specific safety requirements a process or product must meet, often used alongside CTQ in regulated or safety-critical industries.
• Stakeholder Analysis: identifies everyone with influence over, or impact from, the project, and maps out how to manage and communicate with each of them.
• 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 is about establishing a factual, data-driven baseline for how the process currently performs, 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 exactly what data will be collected, how, by whom, and how often, before data collection starts, so the team isn’t stuck reworking a messy dataset later.
• Check Sheet: a simple, structured form for collecting and tallying data by hand at the point where it occurs, often the first real 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 frequently different value ranges occur in a dataset, the fastest way to see a process’s shape, center, and spread at a glance.
• Pareto Chart: a bar chart ranking causes or categories by frequency or impact, built around the 80/20 rule that a small number of causes usually drive most of the problem.
• Box Plots: a compact visual summary of a dataset’s median, quartiles, and outliers, especially useful for comparing the spread of several groups side by side.
• Measurement Systems Analysis (MSA): verifies that your measurement system itself (the gauge, the method, the people doing the measuring) is accurate and consistent enough to trust the data it produces.
• Gage R&R: a specific MSA study quantifying how much of your measurement variation comes from the gauge itself (repeatability) versus the people using it (reproducibility).
• Control Charts: time-ordered plots that distinguish normal, expected process variation from unusual, special-cause variation that needs investigation. See also the specific chart types: I-MR, XmR, and EWMA.
• Process Capability (Cp & Cpk): quantifies whether a process, running as it currently does, is capable of consistently meeting customer specification limits.

Analyze Phase Tools

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

• Cause and Effect Diagram (Fishbone/Ishikawa): a structured brainstorming tool that organizes potential causes of a problem into categories (commonly the 6Ms), branching 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 identifying the true, underlying cause of a problem rather than treating its symptoms, usually using a combination of the tools on this page.
• Failure Mode Effects Analysis (FMEA): a systematic risk-assessment tool that scores potential failure modes by severity, occurrence, and detection, to prioritize which risks need action first.
• Hypothesis Testing: the statistical framework for determining whether an observed difference in your data is a real effect or could just as easily be explained by chance.
• Regression Analysis: a statistical method for modeling the relationship between an input (or inputs) and an output, quantifying how much the output actually moves when the input changes.
• Scatter Diagrams: a quick visual plot of two variables against each other, often the first check for a potential relationship before running a formal regression.
• Multi-Vari Study: a structured way to observe a process without changing anything, to narrow down which family of variation (within-unit, between-unit, or over-time) is driving the problem.
• Cause and Effect Matrix (X-Y Diagram): a scoring matrix that ranks potential input variables (X’s) against how strongly each one affects the key outputs (Y’s) the customer cares about.
• TRIZ: a structured problem-solving method built from patterns found across thousands of patented inventions, used to find creative solutions that resolve a contradiction rather than compromise on it.

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 tends to split into two families of tools: structured creativity tools that help a team generate and organize candidate solutions (Affinity Diagram, Tree Diagram), and verification tools that confirm a solution actually works at small scale before committing to it everywhere (DOE, a pilot run).

• Design of Experiments (DOE): a structured, statistically rigorous way to test multiple factors at once and determine which ones, and which combinations, actually drive the outcome.
• Value Stream Mapping: maps the full end-to-end flow of material and information needed to deliver a product or service, specifically to separate value-added steps from waste.
• Kaizen: a focused, rapid-improvement event (or a broader philosophy of continuous small improvements) aimed at eliminating a specific source of waste quickly.
• Poka-Yoke (Error-Proofing): designs a process or product so that a specific mistake becomes physically impossible, or is caught immediately, rather than relying on inspection after the fact.
• 5S: a workplace organization method (Sort, Set in Order, Shine, Standardize, Sustain) that removes clutter and variation from the physical or digital 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 a large number of individually-generated ideas into natural groupings, useful for making sense of brainstorming output on an unfamiliar problem.
• Interrelationship Digraph: maps the cause-and-effect relationships between multiple interconnected issues, to find which ones are true root drivers versus downstream effects.
• Prioritization Matrix: scores and ranks competing options or projects against a shared set of weighted criteria, to focus effort where it has the most impact.
• House of Quality (QFD): translates customer requirements into specific engineering or design characteristics, making sure what gets built actually maps back to what the customer asked for.

Control Phase Tools

The Control phase locks in the gains from the Improve phase, so the process doesn’t quietly drift back to its old behavior once the project team moves on. This is the phase most likely to get shortchanged under deadline pressure, which is exactly backwards: a fix with no monitoring plan behind it is a temporary fix, not a permanent one, no matter how good the underlying solution was.

• Control Plan: documents exactly how the new process will be monitored going forward, who owns each check, how often, and what to do if a measurement goes out of range.
• Statistical Process Control (SPC): the ongoing practice of using control charts to monitor a live process and distinguish normal variation from a real, actionable shift.
• Standard Work: documents the current best-known way to perform a task, so the improvement is actually followed consistently rather than left to individual habit.
• Response Plan: a specific IASSC-named control-phase tool, a predefined action plan for what to do the moment a monitored metric goes out of control, so the team isn’t improvising under pressure.

Lean Tools (Used Across Every Phase)

Lean tools focus specifically on eliminating waste and improving flow, and they show up throughout a Lean Six Sigma project rather than in one single DMAIC phase. Where the DMAIC tools above are generally diagnostic, figuring out what’s wrong and proving it statistically, Lean tools are generally prescriptive, built to directly remove a known category of waste once you’ve found it. That’s why you’ll often see a Lean tool paired with a DMAIC tool in the same project: a Spaghetti Diagram (Lean) might reveal the wasted motion, and a revised Process Map (DMAIC) documents the fix.

• Classic Wastes (the 8 Wastes): the standard Lean checklist of waste categories (often remembered with the acronym TIMWOODS), used to train your eye to spot non-value-added activity.
• Kanban: a visual signaling system that pulls work through a process based on actual downstream demand, instead of pushing work based on a forecast.
• Spaghetti Diagram: traces the physical path a person, part, or document actually takes through a workspace, which usually exposes an absurd amount of unnecessary travel at a glance.
• 8D Method: an 8-step, team-based problem-solving method, common in the automotive and manufacturing world, that runs from containing a problem through to preventing its recurrence.

The Tools You’ll Actually Use Most Often

Every one of these Six Sigma tools earns its place in a BOK somewhere, but in practice, a small handful carry a disproportionate share of real projects. If you only had time to master five tools before walking into a project (not an exam, a real one), practitioners consistently point to the same short list:

• Process Mapping, because almost nothing else is possible until the team agrees on how the process actually works today, not how it’s assumed to work.
• Cause and Effect (Fishbone) Diagram, because it’s the fastest, lowest-cost way to get a team’s collective knowledge about a problem onto one page before reaching for 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’re the one tool that follows a process from Measure all the way through Control, from baselining it to proving 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 not a reason to skip the rest of the tools on this page, a project involving a true root-cause statistical question will absolutely need Hypothesis Testing or DOE, and a project with a safety or planning dimension will need the more qualitative Improve-phase tools. But if you’re newer to Six Sigma and feeling overwhelmed by the full list, those five are the ones worth getting genuinely comfortable with first.

The Classic “7 Tools” Sets

Two specific groupings of Six Sigma tools show up by name on nearly every Six Sigma and Lean certification exam, worth knowing as named sets, not just individual tools.

• The 7 Basic Quality Tools: the original quality-control toolkit, 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 built for planning and organizing complex, non-numerical problems, Affinity Diagram, Interrelationship Digraph, Tree Diagram, Prioritization Matrix, Matrix Diagram, Process Decision Program Chart (PDPC), and Activity Network Diagram.

Choosing the Right Tool

With this many Six Sigma tools available, the real skill isn’t memorizing every one, it’s knowing which tool fits the question you’re actually 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, it starts with a Project Charter to pin down the scope (which queue, which customers, what counts as “too slow”) and 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 at no point did the team need all 40-plus tools on this page, they needed about seven, in a specific order, each answering a specific question.

Most real projects don’t use every tool on this page, they use the handful that actually answer the specific question in front of the team at that moment. If you’re studying for a certification exam, your belt’s body of knowledge will tell you exactly which of these Six Sigma tools you’re responsible for knowing in depth versus just recognizing by name, a Yellow Belt is typically expected to recognize most of the tools on this page, while a Black Belt is expected to actually execute 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 tool lists, and some tools overlap heavily with general project-management or Lean practice rather than being unique to Six Sigma. This page covers roughly 40 of the most commonly taught Six Sigma tools, organized by the DMAIC phase where each is most often introduced, which covers the large majority of what any certification body will actually 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 are taught most of the tools on this page, but a Black Belt is expected to run the more advanced statistical tools independently, multi-factor Design of Experiments, more advanced regression and ANOVA work, and some of the less common hypothesis tests, where a Green Belt is typically taught to run and interpret 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 are generally built to reduce variation and defects through data and statistics; Lean tools are generally built to reduce waste and improve flow, often without needing statistics at all. A combined Lean Six Sigma project, the most common approach taught on this site, draws from both toolkits depending on whether the problem is a variation problem or a flow/waste problem.