Flowchart Symbols and Meanings: The 10 Standard Shapes Explained
Not sure when to use a rectangle versus a diamond? Flowchart symbols are a shared visual language — using them incorrectly means your diagram can mislead the very people it is meant to help.
This guide covers the 10 standard symbols defined in ISO 5807 (JIS X 0121 in Japan), with a reference table, usage rules, a worked example, and the most common mistakes to avoid.
What you will learn
- A reference table of the 10 standard flowchart symbols
- How to use the 4 essential shapes correctly
- A worked example combining multiple symbols
- 3 common symbol mistakes and how to avoid them
The 10 Standard Flowchart Symbols at a Glance
Flowchart symbols are standardized in ISO 5807 (JIS X 0121 in Japan). In practice, these 10 shapes cover almost every diagram you will ever need. The first four account for more than 80% of real-world usage.
| Symbol | Shape | Meaning |
|---|---|---|
| Terminator | Rounded rectangle / oval | Start and end of the flow |
| Process | Rectangle | A single task or action |
| Decision | Diamond | A conditional branch (Yes/No) |
| Flow line | Solid arrow | Order and direction of steps |
| Data (I/O) | Parallelogram | Data input or output |
| Document | Rectangle with wavy base | A paper or PDF output such as an invoice |
| Preparation | Hexagon | Setup or initialization before the main steps |
| Predefined process | Rectangle with double side bars | A subroutine detailed in another diagram |
| Loop limit | Paired trapezoid-like shapes | Start and end of a repeated block |
| Connector | Small circle | Links flow lines across pages or around crossings |
The 4 Essential Symbols and How to Use Them
- Terminator: mark exactly one start; multiple ends are fine when branches finish differently
- Process: write one verb-led task per rectangle — never bundle several actions into one box
- Decision: phrase the condition as a question ("In stock?") and label every outgoing arrow (Yes/No)
- Flow line: keep the flow in one direction (top to bottom); reserve upward arrows for rework loops
A Worked Example Using the Symbols
Here is an invoicing flow that combines terminators, a data input, a predefined process, a decision, and plain processes. Notice how the shapes alone convey the nature of each step.
In Mermaid notation, ([text]) is a terminator, [text] a process, {text} a decision, [/text/] a data symbol, and [[text]] a predefined process — so the standard shapes map directly to text syntax.
3 Common Symbol Mistakes
- Confusing process and decision: "check inventory" is a process (rectangle); "in stock?" is the decision (diamond) that follows it
- Omitting terminators: without a clear start and end, readers cannot tell where the flow begins or finishes
- Inventing custom shapes: decorative clouds and stars make readers hunt for meaning — stick to the standard set and use color for emphasis
Once you know the symbols, the fastest way to apply them is with a dedicated tool. In DrillSpark, describe your process in plain language and AI drafts a correctly-shaped flowchart in about 30 seconds — symbol choice and layout are handled for you, and the free plan lets you try it right away.