Flowchart Symbols Explained: What Each Shape Means

Every shape in a flowchart has a specific meaning. Use the wrong one and your diagram says something you didn’t intend. Use them correctly and anyone — even someone who’s never seen your process — can follow the logic at a glance.

This is the complete reference. Seven standard shapes, what each one means, when to use it, and the mistakes people make. Bookmark it and open the Flowchart Maker to practice as you read.

1. Rectangle — Process Step

The rectangle is the workhorse of every flowchart. It represents a single action or operation — something that happens. “Send email,” “Calculate total,” “Update database,” “Review application.”

When to use it: Any time you’re describing an action that doesn’t involve a question or a choice. If the step does something, it’s a rectangle.

Common mistake: Cramming multiple actions into one rectangle. “Review application, check references, and schedule interview” is three steps pretending to be one. Each action gets its own box.

2. Diamond — Decision

The diamond represents a yes/no question or a branching condition. It always has at least two arrows coming out of it — one for each possible answer. “Is the payment valid?” “Does the user have an account?” “Is inventory below threshold?”

When to use it: Every time the flow splits based on a condition. The question inside the diamond must have clear, distinct answers — typically “Yes/No” or “True/False.”

Common mistake: Forgetting to label the outgoing arrows. A diamond with unlabeled branches is useless. The reader can’t tell which path is “yes” and which is “no.” Always label both.

Another mistake: putting non-binary decisions in a diamond. If you have three or more outcomes (“High / Medium / Low”), either use multiple sequential diamonds or switch to a different notation.

3. Oval (Rounded Rectangle) — Terminal

Ovals mark the start and end of a flowchart. A flowchart should have exactly one start terminal and at least one end terminal. Labels are typically “Start,” “End,” “Begin,” or something specific like “Order Placed” or “Ticket Closed.”

When to use it: First and last shapes in any flowchart. Period.

Common mistake: Skipping the start terminal and jumping straight into a process rectangle. This makes it unclear where the flow begins, especially in complex diagrams with multiple entry points. Always anchor the flow with an oval at each end.

4. Parallelogram — Input/Output

The parallelogram represents data entering or leaving the system. “Enter username,” “Display results,” “Print report,” “Read sensor data.”

When to use it: Whenever the flowchart interacts with the outside world — receiving input from a user, reading from a file, displaying output on a screen, or sending data to a printer.

Common mistake: Using a rectangle for input/output steps. Technically the flowchart still “works,” but you lose the visual distinction between doing something internally (rectangle) and communicating with the outside (parallelogram). That distinction matters when you’re debugging a process — I/O is where things break.

5. Circle — Connector

A small circle with a letter or number inside is a connector — it links one part of a flowchart to another without drawing a long arrow across the entire diagram. Two circles with the same label (“A” and “A”) mean “the flow continues from here to there.”

When to use it: When a flowchart spans multiple pages or when drawing a direct arrow would create a tangled mess. Connectors keep complex diagrams clean.

Common mistake: Overusing connectors in simple flowcharts. If your diagram fits on one page, draw the arrow directly. Connectors add cognitive overhead — the reader has to hunt for the matching label.

6. Double-Sided Rectangle — Predefined Process

A rectangle with vertical lines on both sides represents a predefined process or subroutine — a set of steps that are documented elsewhere. Think of it as a function call: “Run credit check” or “Execute onboarding flow.”

When to use it: When a step is actually a whole sub-process with its own flowchart. Instead of expanding every detail inline, you reference it. This keeps the current flowchart focused on the big picture.

Common mistake: Using a regular rectangle for subroutines. The double-sided rectangle signals “there’s more detail here, documented separately.” A regular rectangle implies the step is atomic — one action, done.

7. Document Shape — Document Output

The document shape (a rectangle with a wavy bottom edge) represents a physical or digital document that the process produces or references. “Generate invoice,” “Print shipping label,” “Create PDF report.”

When to use it: When the output of a step is specifically a document rather than generic data. It’s a more precise version of the parallelogram — it tells the reader that the output is a tangible artifact, not just data on a screen.

Common mistake: Using this for every output. Reserve it for actual documents. A screen display is a parallelogram. A printed report is a document shape.

Connector Types

Shapes are half the story. The arrows between them carry meaning too:

• Solid arrow — the standard flow connector. “After this step, go here.”
• Dashed arrow — an optional or conditional path. Used less often but helpful for showing exception flows or fallback routes.
• Labeled arrow — any arrow with text on it. Mandatory for decision diamonds (“Yes” / “No”), optional but helpful elsewhere when the transition isn’t obvious.

In the Flowchart Maker, you can switch between straight, elbow (right-angle), and curved connectors. Elbow connectors are the cleanest for most business flowcharts. Curved connectors work well for more organic, brainstorming-style diagrams.

Rules for Using Flowchart Symbols Correctly

Following these rules won’t just make your flowchart “technically correct” — they’ll make it actually useful to the people reading it.

1. Use standard shapes. Don’t invent your own. The whole point of standard symbols is that everyone recognizes them. A reader shouldn’t need a legend to decode your diagram.
2. One entry, one exit per shape. Every shape should have one arrow coming in and one going out, except for decisions (one in, two+ out) and terminals (start has no input, end has no output).
3. Flow top to bottom, left to right. This follows natural reading order. Upward arrows or right-to-left flows are disorienting.
4. Label every decision branch. No exceptions.
5. Keep text short. Two to five words per shape. If you need a paragraph, you’re documenting at the wrong level — the detail belongs in a separate document, not inside the flowchart shape.
6. Use consistent sizing. All rectangles should be the same width. All diamonds the same size. Inconsistent sizing looks amateur and can imply (incorrectly) that bigger shapes are more important.

ISO 5807: The Official Standard

These shapes aren’t arbitrary conventions. They’re defined by ISO 5807, the international standard for information processing documentation symbols. Published in 1985 and still the reference today, ISO 5807 standardized the shapes so flowcharts are universally readable, regardless of who created them or what industry they’re in.

You don’t need to read the standard — every shape described above follows it. Just know that when someone says “use standard flowchart symbols,” this is what they mean.

Build One Now

Open the Flowchart Maker and try building a simple flow using all seven shapes. A good practice exercise: diagram your morning routine from alarm to leaving the house. You’ll use terminals (start/end), processes (shower, eat), decisions (snooze or get up?), and I/O (check phone). If you need a more complex canvas, the Diagram Maker supports additional shape types and layered diagrams. For freeform sketching before you commit to structure, try the Whiteboard.