What Is Lean Six Sigma? A Practical Guide for SMEs

6 min read · Updated July 2026

Lean Six Sigma is a proven, practical approach to improving how work gets done — cutting waste, reducing errors and delivering more value to customers. This guide explains what it is, where it came from, and how a small or mid-sized business can put it to work.

Lean vs Six Sigma: two ideas, one method

Lean is about speed and flow: it removes anything that slows work down or adds cost without adding value. Six Sigma is about consistency: it reduces variation and defects so a process delivers the same good result every time. Combined, "Lean Six Sigma" gives you both — faster processes that are also reliable.

Lean grew out of the Toyota Production System in post-war Japan. Six Sigma was developed at Motorola in the 1980s and popularised by GE in the 1990s. Today they are used together across manufacturing, healthcare, logistics, financial services and the public sector.

The core idea: value, waste and variation

Every process exists to deliver value to a customer. Anything that consumes time or money without adding value is waste. Lean practitioners look for eight classic wastes (often remembered as "TIMWOODS"):

• Transport — moving materials or information unnecessarily
• Inventory — more stock or work-in-progress than needed
• Motion — unnecessary movement of people
• Waiting — idle time between steps
• Overproduction — making more, or sooner, than required
• Overprocessing — doing more work than the customer values
• Defects — errors, rework and scrap
• Skills — underusing people’s knowledge and ideas

Six Sigma adds a focus on variation. Even a process with little visible waste can produce inconsistent results; reducing that variation is what makes quality dependable.

How improvement happens: DMAIC

Improvement projects follow a five-phase cycle called DMAIC — Define, Measure, Analyse, Improve and Control. It keeps teams disciplined: understand the problem and measure it before jumping to solutions, then lock in the gains so they last.

Belts: who does what

Practitioners are trained to "belt" levels borrowed from martial arts — White, Yellow, Green, Black and Master Black Belt — reflecting how much they can lead. You do not need a black belt to start improving; awareness training is enough to contribute.

Where to start as an SME

You do not need certification or a big programme to begin. Start by understanding your current maturity, pick one genuinely painful process, and run a small, well-scoped DMAIC project. A structured diagnostic is the quickest way to see where the biggest gains are.