What is a Pugh matrix?
The Pugh matrix is a concept selection method for the early stages of design, when concepts are sketches rather than detailed designs and precise scores would be false precision. Instead, each concept is compared with a datum on each criterion: is it better, the same or worse? The pattern of pluses and minuses shows where each concept is strong, and the discussion it triggers is often more valuable than the final number.
The Pugh method
- Agree the criteria from the customer and design requirements, with weights if they differ in importance.
- Sketch the concepts to the same level of detail.
- Choose a datum: the current design or a strong candidate.
- Compare each concept with the datum: +, S or −.
- Analyse the totals and the minuses of the best concepts.
- Improve and iterate: build hybrids, change the datum and repeat.
Pugh matrix example
A team designing a new sample tube cap compares four concepts with the current screw cap on six weighted criteria. The push-fit cap scores best (weighted net +6): easier to open with gloves, cheaper and compatible with the automated decapper, but less leak-tight. The septum cap (+5) is the most leak-tight but costs more and does not withstand sterilization as well. The team's next round tests a hybrid: a push-fit cap with the septum cap's sealing lip, with the push-fit cap as the new datum.
Related tools
- Decision matrix: absolute weighted scores for later-stage choices.
- Prioritization matrix: weights from pairwise comparison.
- FMEA: analyse the risks of the selected concept.
How to use this Pugh Matrix tool
- State the decision. Write what the concepts are for.
- List the criteria. Add the criteria from the requirements and weight each from 1 to 5.
- Add the concepts. Add each concept as a column and choose one as the datum (baseline).
- Compare with the datum. Click each cell: + better, S same, − worse than the datum on that criterion.
- Read the totals. The matrix sums plus, minus and S, and ranks the concepts by weighted net score.
- Improve and repeat. Combine strengths into a hybrid, make the best concept the new datum, and export each round to PDF or Excel.
Frequently asked questions
What is a Pugh matrix?
A Pugh matrix (Pugh concept selection, or decision-matrix method) compares several design concepts against one reference concept, the datum. For each criterion, each concept is rated better (+), the same (S) or worse (−) than the datum. The counts of plus and minus show the strengths and weaknesses of each concept. It was developed by Stuart Pugh at the University of Strathclyde.
What is the datum in a Pugh matrix?
The datum is the baseline every concept is compared against: usually the current design, a competitor product or one of the concepts. The datum column is all S by definition. Changing the datum and repeating the comparison is part of the method.
How do you score a Pugh matrix?
Count the pluses, minuses and S for each concept. The net score is pluses minus minuses. With weights (1 to 5) for the criteria, the weighted net score is the sum of weight × (+1, 0 or −1). This tool shows both and ranks the concepts by the weighted net score.
Is the highest score the winner?
Not necessarily. Pugh intended the matrix to improve concepts, not just pick one: look at why the best concepts score minus on some criteria and whether ideas from other concepts can fix those weaknesses. Build a hybrid, make it the new datum and repeat until the concepts converge.
What is the difference between a Pugh matrix and a decision matrix?
A Pugh matrix uses relative judgements (better, same, worse than a datum) and is used early in design when concepts are not detailed enough for absolute scores. A weighted decision matrix uses absolute scores and suits later decisions such as supplier or equipment selection.
Where is the Pugh matrix used?
In product design and Design for Six Sigma, in engineering concept selection, and in process improvement to choose between solutions. It is often documented as part of design control and design review records.