What is a dimension in Tableau and BI?
Quick answer
A dimension is a field that describes or categorizes your data, such as region, product, customer or order date. In a chart, dimensions decide how the data is split: one bar, row or line per value. They answer the "by what?" in "revenue by region".
Last updated
Updated · By Robert Breen
Why it matters
Every business question has a "by" in it: sales by month, tickets by team, spend by channel. The dimension is that "by". Choosing the right one is most of the work of building a useful chart.
BI tools treat dimensions and measures differently. Dimensions get grouped; measures get summed or averaged. When a tool guesses wrong, you get either a single meaningless total or thousands of tiny marks.
A worked example
An HR team has a table of 260 employees with Department, Office, Hire date and Salary. Department, Office and Hire date are dimensions. Put Department on a bar chart and you get one bar per department (Sales, Finance, Engineering, and so on), each showing the aggregated salary measure.
Employee ID is stored as a number, so Tableau first lists it with the measures. Summing employee IDs gives 1,852,730, which means nothing. Converting Employee ID to a dimension gives one mark per person, which is what a headcount chart needs (with COUNTD of Employee ID as the measure).
Often confused with
Dimension vs measure
Dimensions slice and label. Measures are the numbers being summarized. A quick test: if adding two values together makes sense, it is a measure.
Dimension vs discrete
In Tableau, "discrete" (blue) and "continuous" (green) are about how a field draws: headers or an axis. Most dimensions are discrete, but a date dimension can be continuous to make a timeline.
Dimension in a data warehouse
In data warehouse design, a "dimension table" holds descriptive details (customers, products) that join to a table of transactions. It is the same idea at the database level.
Tips
- Convert IDs, ZIP codes and phone numbers to dimensions as soon as you connect data.
- Use the fewest dimensions that answer the question; each extra one multiplies the marks on a chart.
- For time, pick the level people decide at: week for operations, month for finance.
Related terms
Learn it in a free lesson
- What Is Business Intelligence? A Beginner’s Guide (about 8 minutes)
- Dimensions vs Measures in Tableau, With Examples (about 9 minutes)
- Tableau Public Tutorial: Your First Chart and Dashboard (about 15 minutes)
Questions about it
- Should I learn Tableau or Power BI first?: Learn the BI tool your employer, or the one you want, uses. If none, Tableau on a Mac or Power BI on Windows. The core ideas transfer…
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Frequently asked questions
- Is a date a dimension or a measure?
- A dimension. You group by dates (by day, week or month). In Tableau it can be drawn as discrete headers or as a continuous timeline.
- Why does Tableau put my ID column under measures?
- Because it is stored as a number. Right-click it and choose Convert to Dimension.
- Can a field be both?
- Sometimes. Age can be a dimension (to group people into ages) or a measure (to average it). Decide based on the question.
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