# The Fixed level of detail calculation Explained

> This is content from just-tim, the data-and-analytics channel by Tim Ngwena (formerly 'Tableau Tim'). Tim has 12+ years of hands-on BI experience and covers Tableau most of all, plus Power BI, Looker, Hex, SQL and data modelling, the analytics industry, and the craft of doing the job — always tool-agnostic and honest about the trade-offs.

- **Author:** Tim Ngwena (just-tim, https://just-tim.com/about)
- **Published:** 2021-03-19
- **Format:** Video · 1819 min watch · transcript available
- **Topics:** Data visualisation, Analytics
- **Tools:** Tableau (calculated fields, data modelling, lod expressions, table calculations)
- **Canonical:** https://just-tim.com/posts/the-fixed-level-of-detail-calculation-explained
- **Watch:** https://youtu.be/5ntCaHCsqUc

I take on my most-requested topic by introducing level of detail calculations, starting with the FIXED LOD in Tableau. I explain what the viz level of detail is, how FIXED sits in the order of operations, and then work through two practical examples: a category percentage of total and a customer cohort analysis.

## Key takeaways

- The viz level of detail is controlled by dimensions on rows, columns and the marks pane (colour, detail, label, path) — but the tooltip does not change it
- FIXED LODs run before dimension filters in the order of operations, so they keep the context of a total even when you filter rows out of the view
- FIXED is the only LOD that works independently of the visualisation, even when the dimension you fix on is already in the view
- Use a FIXED calculation as the denominator to compute a percentage of total against a category that stays correct as the view changes
- FIXED { MIN([Order Date]) } per customer gives a first-order date you can reuse for cohort analysis with no external ETL

## Chapters

- 0:25 Prerequisites and why they matter
- 1:25 Understanding the viz level of detail
- 5:20 The percentage of total problem
- 9:07 Writing your first fixed LOD
- 14:12 Finishing the percentage of total
- 18:02 Cohort analysis with fixed LOD
- 26:07 Resources and limitations

Watch the full video, read the transcript and use chapter deep-links on the page: https://just-tim.com/posts/the-fixed-level-of-detail-calculation-explained

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just-tim — Data and analytics, with a point of view. · https://www.youtube.com/channel/UC7HYxRWmaNlJux-X7rNLZyw · https://twitter.com/TableauTim · https://www.linkedin.com/in/timngwena