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Calculations: Converting from nanograms to copy number

Researchers performing qPCR will often create a standard curve based on nanograms of amplicon, and then need to convert the resulting nanograms detected to copy number. The formula for making this conversion is as follows:


X = amount of amplicon (ng)
N = length of dsDNA amplicon
660 g/mole = average mass of 1 bp dsDNA

The actual oligonucleotide MW (in Daltons or g/mole) is provided on the IDT Spec Sheet for each oligonucleotide and can be substituted for this arithmetic phrase, which only provides an average MW for a sequence of this length.

An alternative is to create the standard curve based on copy number; e.g., ranging from 100 to 107 copies, in 10-fold increments. You can then determine copy number directly from the standard curve.

Let free software do it for you!

A convenient, free-access copy number calculator was developed by former IDT customer, Andrew Staroscik, who has since left the bench. The calculator can be found at: http://www.scienceprimer.com/copy-number-calculator-for-realtime-pcr.

Additional reading

Read more articles about handling oligos in our Oligo Handling and Applications section. Here are some examples of what you will find there:

Troubleshooting Polyacrylamide Gel Electrophoresis (PAGE)—Our gel electrophoresis team provides an extensive troubleshooting guide for the PAGE issues they have come across during their work.

 RxnReady Oligos—Get Your Oligos Premixed!—Have 2–6 standard desalted DNA oligonucleotides premixed in a single tube according to your specifications. This can be useful when performing multiplex PCR, or when generating sets of insertions or deletions through site-directed mutagenesis. 

Understanding Melting Temperature (Tm)—Advice from our own Dr Richard Owczarzy on considerations for better oligo design: oligo concentration, salt, SNPs. 


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