Iso Standard Flowchart Symbol Reference Chart and Meanings

Most people who draw flowcharts guess their way through the symbols. They pick a rectangle for everything, throw in some arrows, and hope the meaning is clear. It usually isn't. That's exactly why an ISO standard flowchart symbol reference chart exists it gives everyone a shared set of shapes and definitions so diagrams actually communicate what they're supposed to. If you've ever opened someone else's flowchart and felt confused, the problem was probably non-standard symbols.

What is an ISO standard flowchart symbol reference chart?

An ISO standard flowchart symbol reference chart is a visual guide showing the officially recognized shapes used in flowcharts according to ISO 5807:1985 the international standard for documentation symbols and conventions used in data processing and program flowcharts. The International Organization for Standardization published this standard to eliminate the confusion that happens when different teams invent their own diagramming conventions.

The chart typically includes shapes like rectangles for processes, diamonds for decisions, parallelograms for input/output, ovals for terminal points, and several others. Each shape has a defined meaning, and using them consistently is what separates a professional flowchart from a messy sketch on a whiteboard. You can learn more about the basic flowchart shapes and how they work before diving into the full ISO set.

Why does following the ISO standard matter for flowcharts?

Flowcharts are communication tools. When you use non-standard symbols, you force every reader to guess what you mean. This creates real problems in software development, business process mapping, engineering, and quality management fields where miscommunication can cost time and money.

ISO 5807 solves this by giving you a common language. Here's what that means in practice:

Cross-team clarity: A developer in Germany and a project manager in Japan can read the same flowchart without confusion.
Audit readiness: Regulated industries like healthcare, aviation, and finance expect documentation that follows recognized standards.
Faster onboarding: New team members understand existing process maps without needing someone to explain each symbol.
Tool compatibility: Major diagramming software like Microsoft Visio, Lucidchart, and draw.io all include ISO-compliant symbol libraries.

What symbols are included in the ISO 5807 reference chart?

The standard defines several categories of symbols. Here are the most commonly used ones:

Basic flowchart symbols

Terminal (Oval/Rounded Rectangle): Marks the start or end of a process. Sometimes called a "terminator."
Process (Rectangle): Represents a single step, action, or operation in the flow.
Decision (Diamond): Shows a point where the flow branches based on a yes/no or true/false condition. Getting the decision diamond symbol right is critical for accurate logic flow.
Input/Output (Parallelogram): Indicates data entering or leaving the process user input, file reads, printed output, etc.
Flow Line (Arrow): Connects symbols and shows the direction of the process flow.

Additional ISO symbols

Predefined Process (Rectangle with double vertical lines): Refers to a process defined elsewhere, like a subroutine or a separate document.
Preparation/Initialization (Hexagon or elongated hexagon): Represents setup steps such as initializing variables or setting initial values.
Manual Operation (Trapezoid): A step performed by a person, not a computer.
Connector (Small circle): Used to link parts of a flowchart that span multiple pages or break across a large diagram.
Off-Page Connector (Pentagon): Points to a continuation on a different page.
Document (Rectangle with a wavy bottom line): Indicates a printed document or report is generated or referenced.
Storage (Open-ended rectangle or cylinder): Represents data stored in a database or file system.
Display (Rectangle with one curved side): Shows output displayed on a screen.

For a deeper breakdown of what each shape means and how to use it correctly, our flowchart symbols meaning and usage guide covers every detail.

When should you use an ISO standard flowchart symbol reference chart?

You don't need to memorize every symbol you need to know when reaching for the reference chart actually helps. Here are situations where it matters most:

Creating documentation for regulated industries where auditors expect ISO-compliant processes.
Working on cross-functional projects where different departments need to read the same diagrams.
Building software architecture diagrams that developers across time zones will implement.
Writing standard operating procedures (SOPs) that include visual process maps.
Teaching or training instructors and trainers use the chart to teach correct diagramming to students.
Quality management systems (QMS) like ISO 9001 often include flowcharts in their documentation, and using standard symbols adds credibility.

What are the most common mistakes people make with flowchart symbols?

Even experienced professionals get some of these wrong. Here are the frequent errors:

Using rectangles for everything. The process box is versatile, but if your flowchart only uses rectangles, readers can't tell decisions from steps from inputs at a glance.
Skipping the start and end terminals. A flowchart without clear entry and exit points leaves readers wondering where the process begins and ends.
Mixing symbol styles inconsistently. If your diamond is sometimes filled, sometimes outlined, and sometimes a different size, it creates visual noise.
Using connector symbols when you don't need them. Connectors help in long, multi-page diagrams. Using them in a simple 10-step flowchart adds unnecessary complexity.
Confusing the parallelogram (I/O) with the rectangle (process). They look similar at a glance, but they mean different things. Slightly tilting the I/O box makes the distinction clear.
Arrows that go in unclear directions. Every arrow should flow logically top to bottom or left to right. Crossed or looping arrows confuse readers fast.

How does ISO 5807 relate to other flowchart standards?

ISO 5807 isn't the only standard that defines flowchart symbols, but it's the most widely referenced for general-purpose data processing and program flowcharts. Other related standards include:

ANSI X3.5: The American National Standards Institute version, which largely overlaps with ISO 5807 but has minor differences in some symbol definitions.
BS 4058: The British Standard for flowchart symbols, again very similar to ISO 5807.
IEC 61131-3: Covers programming languages for programmable controllers and includes specific diagram conventions for industrial automation.

For most practical purposes, ISO 5807 and ANSI X3.5 are interchangeable. If your organization uses one, you're essentially compliant with the other. The important thing is to pick one standard and stick with it across all your documentation.

Where can you find an ISO standard flowchart symbol reference chart?

You have a few options for getting your hands on a usable reference chart:

Official ISO documentation: You can purchase ISO 5807:1985 directly from the ISO website. It's the authoritative source, though it reads more like a technical specification than a quick reference.
Diagramming software libraries: Tools like Visio, Lucidchart, Draw.io, and SmartDraw all include built-in ISO symbol libraries. These are often the most practical option because you can drag and drop symbols directly.
Quick reference cheat sheets: Many project management and software development sites publish printable symbol charts. These work well pinned next to your desk or saved as a desktop image.
Template libraries: Sites like Canva, Notion, and various BPM tools offer pre-built flowchart templates that already use ISO-standard symbols.

Practical tips for using your reference chart effectively

Keep a printed or digital copy open while you diagram don't rely on memory.
Use the same tool's symbol library consistently rather than mixing shapes from different software.
Label every symbol clearly. Even the right shape loses meaning if the text inside is vague.
Limit your flowchart to one clear path per decision branch. If a diamond has more than two outputs, consider splitting it.
Review your flowchart with someone who didn't create it. If they can follow it without explanation, your symbols are working.
For long processes, use on-page and off-page connectors rather than making the chart unreadably small.

Quick reference checklist before you publish any flowchart

Run through this checklist every time you create or review a flowchart:

Does every flowchart have a clear start and end terminal?
Are all process steps in rectangles?
Is every decision point a diamond with clearly labeled branches?
Are inputs and outputs shown in parallelograms, distinct from process boxes?
Do all arrows flow in one consistent direction (top-to-bottom or left-to-right)?
Are predefined processes and documents using their correct ISO shapes?
Is the chart readable at normal zoom without squinting or scrolling?
Would someone unfamiliar with the project understand the flow without your help?

Print this list. Save it to your desktop. Use it every time. Standard symbols only help when you actually use them correctly and this checklist keeps you honest.