How do I determine the mass of my oligonucleotide?

The molecular weight of your oligonucleotide is provided on the Certificate of Analysis. Multiply that number by the number of μmoles. For example, if the molecular weight of your oligonucleotide is 6950 au, and you have 0.2 μmoles of product, you have 1390 μg or 1.39 mg.