Oligo and primer resuspension from nmol to µM
An oligonucleotide amount reported in nmol can be converted directly to a µM stock volume because 1 nmol equals 1,000 pmol and 1 µM equals 1 pmol/µL.
The calculator determines volume only. Confirm the supplied amount, chemical modifications, recommended diluent, mixing, storage, and stability instructions on the product documentation.
How to calculate oligo resuspension volume
- Confirm the amount: Use the nmol amount applicable to the delivered oligo and supplier documentation.
- Choose stock concentration: Enter the desired concentration in µM.
- Calculate volume: Read the required final resuspension volume in µL.
- Follow product guidance: Use the supplier-approved diluent, resuspension, storage, and handling procedure.
Formula and variables
The factor 1,000 converts nmol to pmol, while µM is numerically equivalent to pmol/µL.
V (µL) = amount (nmol) × 1000 / concentration (µM)- V — Resuspension volume
- Calculated final stock volume (µL)
- n — Oligo amount
- Amount stated by the supplier or certificate (nmol)
- C — Target stock concentration
- Desired molar concentration of oligo molecules (µM)
Prepare a 100 µM primer stock
A tube contains 25 nmol of dried oligonucleotide.
- Amount
- 25 nmol
- Target
- 100 µM
- V = 25 × 1000/100
Result: The calculated final resuspension volume is 250 µL.
At that final volume, the ideal concentration is 100 pmol/µL, equivalent to 100 µM.
Understanding your results
The result is a molar concentration calculation
It assumes the stated nmol amount is the relevant recoverable oligo amount and the completed solution reaches the calculated volume.
- 100 µM equals 100 pmol/µL.
- A larger volume produces a lower concentration.
- A smaller volume produces a higher concentration.
- Mass concentration requires molecular weight and is a different calculation.
Assumptions
- The reported oligo amount is accurate and applicable to the intended stock.
- The oligo is fully resuspended without loss.
- Target concentration refers to oligo molecules in µM.
Limitations
- Does not correct for recovery, purity, salt form, water content, adsorption, or evaporation.
- Does not choose diluent, storage temperature, or handling conditions.
- Does not convert absorbance or mass into nmol.
Common mistakes
- Treating nmol as ng.
- Confusing µM with ng/µL.
- Using delivered mass instead of the stated molar amount.
- Ignoring supplier guidance for modified or RNA oligos.
Practical use cases
Primer stock preparation
Calculate a common working stock volume from a supplier-reported nmol amount.
Concentration planning
Compare final volumes for different target µM concentrations.
Frequently asked questions
Why is there a factor of 1,000?
One nmol is 1,000 pmol, and one µM is equivalent to one pmol per µL.
What diluent should I use?
Follow the oligo supplier’s instructions for the oligo type, modifications, downstream use, and storage needs.
Is 100 µM the same as 100 ng/µL?
No. Converting molar concentration to mass concentration requires the oligo’s molecular weight.
Sources and review
- How do I resuspend my oligos? — Integrated DNA Technologies. Accessed 2026-07-13.
Reviewed 2026-07-13.