Iso Standard Flowchart Symbol Codes Reference Chart Guide

If you've ever opened a flowchart template and wondered which shape means what or worse, used the wrong symbol and confused your entire team you're not alone. An ISO standard flowchart symbol codes reference chart exists to solve exactly that problem. It maps every approved symbol to its meaning so anyone reading your diagram, anywhere in the world, can follow it without guesswork.

What Are ISO Standard Flowchart Symbol Codes?

Flowchart symbol codes are the standardized shapes and notations defined by the International Organization for Standardization (ISO). The main standard governing these symbols is ISO 5807:1985, which lays out symbols for data processing documentation. These codes assign specific geometric shapes rectangles, diamonds, parallelograms, ovals to specific functions like processes, decisions, inputs, and outputs.

When everyone uses the same symbols, a flowchart created in Tokyo reads just as clearly in São Paulo. That consistency is the whole point. If you want a deeper breakdown of each symbol's meaning, we've covered standard flowchart symbol codes explained in detail on another page.

Why Does This Reference Chart Matter?

A reference chart removes ambiguity. Without one, teams tend to invent their own shapes or use software defaults that don't follow any standard. This leads to diagrams that only the creator understands. Here's what a proper reference chart prevents:

Miscommunication between developers, analysts, and stakeholders who interpret symbols differently
Rework caused by diagrams that need to be redrawn once someone points out incorrect notation
Onboarding delays when new team members can't read existing flowcharts

Think of it like a legend on a map. Without the legend, you can guess what the icons mean, but you'll get lost eventually.

Which Symbols Are Included in the ISO Standard?

ISO 5807 defines a set of core symbols that cover most documentation needs. Here are the ones you'll use most often:

Rectangle (Process) Represents a single step, action, or operation in the flow
Diamond (Decision) Indicates a yes/no or true/false branch point
Parallelogram (Input/Output) Shows data entering or leaving the process
Oval or Rounded Rectangle (Terminal) Marks the start or end of a flow
Arrow (Flow Line) Connects symbols and shows the direction of flow
Circle (Connector) Links different parts of a flowchart, especially across pages
Rectangle with double vertical lines (Predefined Process) Refers to a process defined elsewhere
Document Symbol A rectangle with a wavy bottom edge, representing a printed or digital document

You can view a full visual layout of these shapes on our ISO standard flowchart symbol codes reference chart page.

When Should You Use This Reference Chart?

Any time you create, review, or share a flowchart, the reference chart earns its keep. Specific situations include:

Writing software documentation that multiple teams will read
Mapping business processes during audits or compliance reviews
Teaching or training people who are new to flowcharting
Preparing technical proposals that include system diagrams
Collaborating with international teams who expect ISO-compliant notation

Software engineers, in particular, benefit from sticking to the standard. If that's your field, our guide on flowchart symbol codes for software engineering covers the symbols most relevant to code architecture and system design.

What Happens When People Don't Follow the Standard?

The most common mistakes come from improvising. Here's what goes wrong:

Using rectangles for everything. When every shape is a box, decisions, inputs, and outputs all look the same. The reader has to figure out meaning from context clues instead of the shape itself.
Skipping the start/end terminal. A flowchart without clear entry and exit points forces the reader to hunt for where the process begins.
Inconsistent arrow directions. ISO convention flows top-to-bottom or left-to-right. Mixing directions without reason creates confusion.
Overloading a single symbol. A diamond should represent one binary decision. If you're cramming multiple conditions into it, break it into separate decision points.
Ignoring connector symbols on long charts. When a flowchart spans multiple pages, circle connectors keep the flow linked. Leaving them out means readers lose the thread.

How Do You Use the Reference Chart in Practice?

Here's a simple workflow for using your reference chart effectively:

Print or pin the chart near your workspace, or bookmark it digitally if you work on a screen.
Before drawing, list the steps in your process. Identify which ones are decisions, inputs, outputs, or subprocesses.
Match each step to its symbol using the chart.
Draw the flowchart using proper shapes and flow lines.
Review against the chart before sharing. Check that every symbol is the correct one for its function.

This five-step check takes about two minutes and prevents most notation errors.

Tips for Getting the Most Out of Your Flowchart

Keep it to one page if possible. If your flowchart needs more than one page, use connector circles and label them clearly (A1 to A2, B1 to B2, etc.).
Use color sparingly and consistently. Color can highlight paths (like error routes in red), but don't rely on color alone to convey meaning symbols should still follow ISO standards.
Label every arrow leaving a decision diamond. "Yes/No," "True/False," or a specific condition should be written directly on the flow line.
Test readability with someone unfamiliar with the project. If they can follow the flow without your explanation, the chart works.
Use diagramming tools that support ISO symbols. Tools like Microsoft Visio, draw.io, Lucidchart, and yEd include ISO-standard shapes in their libraries.

Does the ISO Standard Ever Get Updated?

ISO 5807 was originally published in 1985 and reaffirmed in recent years. While the core symbols haven't changed, the way people apply them has expanded with new diagramming methods like UML (Unified Modeling Language) and BPMN (Business Process Model and Notation). These aren't replacements for ISO 5807 they're complementary standards used in specific domains. The ISO flowchart symbols remain the baseline for general-purpose process documentation.

If your organization is formal about documentation standards, it's worth checking whether your templates align with the current version of ISO 5807. You can find the official document on the ISO catalog page for ISO 5807.

Quick-Reference Checklist

Use this checklist the next time you create or review a flowchart:

☐ Every process step uses a rectangle
☐ Every decision point uses a diamond with labeled branches
☐ Data inputs and outputs use a parallelogram
☐ The chart starts and ends with a terminal symbol (oval or rounded rectangle)
☐ All arrows flow in one consistent direction (top-to-bottom or left-to-right)
☐ Connector circles link multi-page sections with matching labels
☐ Predefined processes use the double-bordered rectangle
☐ Documents are represented with the wavy-bottom rectangle
☐ The chart was reviewed against the ISO reference chart before distribution