> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/library-preparation/general-library-prep/library-preparation-general-library-prep-reference_material-list/000001240.md).

# Converting ng/µl to nM when calculating dsDNA library concentration

Many standard Illumina libraries, such as Illumina DNA Prep, require the use of dsDNA-specific fluorescent dye methods for accurate quantification. These methods typically measure dsDNA concentration in ng/µl. To convert from ng/µl to nM for cluster generation, follow the instructions below.

1. Determine the average size of the library by running it on an Agilent Technologies TapeStation, 2100 Bioanalyzer, or Fragment Analyzer.
2. Use the following formula to convert from ng/μl to nM:

![](https://761066130-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FGM9W2DuBTgEXv1ClCm8H%2Fuploads%2Fgit-blob-6ccf3d06b43bab779729a9de201f1cf4e7201362%2Fimage1.jpg?alt=media\&token=a79efa39-5616-49d2-bcdb-0ced501d554a)

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #1240), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000001240%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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