Speed-up In Your Projects with The FAST Diagram + Free Template!

Speed-up In Your Projects with The FAST Diagram + Free Template!

By Nathan Cavet & Coralie Petit
Updated: April 5, 2024, first publication: April 2021

There are so many mechanisms to organize your projects. Today, in the family of organization and visualization tools, we ask the FAST diagram to join us!

If you want to detail the development of your product from all angles, in a collaborative, exhaustive and 100% functional way, you've come to the right place!

Today we study the role and importance of this matrix. We give you a quick definition, illustrated examples, issues, and diagram template here! ⤵️

What is a FAST Diagram?

The FAST Method of Design: Definition

First things first, what is the FAST method in design?

FAST, whose initials stand for Function Analysis System Technique, is a structured approach used in product and system design. This concept focuses on identifying and organizing the essential functions.

This method breaks down complex systems into simpler, fundamental functions of the product, hierarchically arranging them to understand dependencies and relationships… such as theFAST diagram

And this diagram is quite unique:

  • constructed from left to right,
  • which represents the logical relationships between different functions,
  • to answer the questions how and why.

In this simplified example:

  • How to inform the reader about the product or the service? → By publishing articles on the web.
  • How? → By using a platform like WordPress.
  • Why should you use WordPress? → To publish articles on the web.
  • Why? → To inform the reader.

What is Functional Analysis?

Functional analysis is a process in product design and engineering where a system or product is broken down into fundamental functions.

The idea is to do an analysis — or understand, of what the product must do, rather than how it does it.

This is one of the deliverables and means used in functional analysis, which aims to determine the architecture of a system, both in industry and in IT. Other deliverables include:

2 FAST Diagram Examples

The first example of a possible FAST diagram:

Sample FAST diagram© ResearchGate

The second example of a possible washing machine FAST diagram:

How ->  <- Why

Stirring the laundry

Rotating the drum

Managing the speed and direction of rotation
Converting electrical energy into mechanical rotation energy
Adapting energy
Distributing energy

☝️ Don't mix up the FAST diagram with the APTE diagram. The APTE diagram is used to represent all constrained functions around the main function:

APTE diagram@ Remy Ducros

The Advantages of The FAST Method

The FAST model starts from the expressed needs and illustrates how to answer them as objectively and exhaustively as possible.

In the context of value-based management, for example for the development or improvement of a product, a process, or a project, it enables engineers to translate services into technical functions, thanks to a good knowledge of the product.

In short, the FAST diagram encourages a creative and collaborative thinking process by allowing to:

  • clearly establish the basis of the project and consider it in its entirety from the designing phase,
  • develop a common understanding of the product within the project team,
  • take into account all the ins and outs of each development,
  • determine the scope of the project, the extent of the tasks to complete it and their interdependence, if any (top-down).

How To Build a FAST Diagram?

4 Steps to Build it Collaboratively

#1 — Do a Functional Analysis 

Functional analysis is crucial, as it identifies and prioritizes a product’s essential functions, streamlining design efficiency and innovation.

This step is what makes clear communication within teams and aligns the product development with user needs and expectations.

But how to make a good functional analysis? ✅

  1. List all the functions of a product, for example, for a washing machine: wash clothes, rinse clothes, spin clothes,
  2. Detail these functions, prioritize them and value them (high or low importance),
  3. Identify the main functions (removing stains), the secondary functions (softening the laundry) and the constrained functions (not damaging the laundry).

#2 — Do The Analysis Each Function

For each function identified:

  • You should ask yourself "How is this function accomplished?" and write the answer to the right, in the form of an active verb and a noun designating something measurable.
  • And then, you should wonder "Why develop this function?" and write the answer on

#3 — Addressing Logic Problems

For each logic problem in the scenario, identify missing or redundant functions or adjust the order of functions as needed for logical coherence.

#4 — Identifying Dependencies and Simultaneities

Identify those that occur simultaneously or depend on each other, by asking:

  • When this function is performed, does another function trigger?
  • Or does it depend on the triggering of another function?

and write the answer below.

There are different methods of using and building an efficient FAST diagram. Some can mention basic function, cost and other components.

A FAST diagram can take many forms, like a tree or even regular lines. The objective is to support the project and to meet future customers expectations or the values expected by clients.

It is up to you to choose what will the content of your FAST diagram describe!

How To Read a FAST Diagram?

Because the FAST diagram is a rather unique, you might be wondering how to actually read it.

But what’s better than a pictured example?

example fast diagram© Value Analysis Canada
  • The main functions, of a higher level, are on the left: they represent why, the need,
  • the technical functions and sub-functions are on their right, of a lower level, they represent the "how to accomplish the main functions, to achieve the desired result",
  • those that have a link are on top of each other, they represent the interdependencies and simultaneity, the when, which is therefore not temporal.

Summary and Template to Download

Still struggling to make your own diagram? 👇

Here is a FAST diagram to fill in, in Word format, starting from a preconceived and blank template.

Note that there are no arrows, you have to indicate them at the appropriate places.

FAST Diagram Free Template


Be Fast With a FAST Diagram

Every project and every diagram are different, so we recommend that you use software that allows you to make a custom FAST diagram online, like a project management or BPM tool to design your diagrams or mind maps more effectively.

What about you, do you use online software to make your FAST diagram faster?

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