NEB Primer Reconstitution & Dilution Calculator
Use this tool to quickly determine how much nuclease-free water (or TE) to add to a lyophilized primer, and how to make a working dilution for PCR setup.
What this NEB primer calculator is for
If you order primers for PCR, qPCR, cloning, mutagenesis, or sequencing, they usually arrive lyophilized with a reported yield in nmol. Before use, you need to reconstitute each primer to a stock concentration and often make a lower working concentration for day-to-day pipetting. This calculator helps you do that quickly and consistently.
While this page is inspired by common workflows used with New England Biolabs protocols, it is a general-purpose oligo calculator and can be used for primers from any vendor.
How the calculations work
1) Reconstitution volume
Primer yield is commonly listed in nmol. Since 1 nmol = 1000 pmol, and 1 µM = 1 pmol/µL:
- Reconstitution volume (µL) = (nmol × 1000) / desired stock concentration (µM)
Example: 25 nmol primer at 100 µM stock gives (25 × 1000) / 100 = 250 µL.
2) Dilution from stock to working solution
Use the standard dilution equation:
- C1V1 = C2V2
- V1 (stock needed) = (C2 × V2) / C1
If your stock is 100 µM and your target working solution is 10 µM, that is a 1:10 dilution.
Practical primer setup workflow
Recommended approach
- Reconstitute each new primer to a stable stock (often 100 µM).
- Create a working tube (often 10 µM) for regular PCR setup.
- Store stocks frozen and avoid frequent freeze-thaw cycles.
- Label clearly with sequence name, concentration, and date.
Why this matters
Pipetting directly from very concentrated stock can increase variability, especially at low microliter volumes. A consistent working concentration makes reaction setup faster, cleaner, and easier to reproduce across users.
Sequence quick-check (optional)
If you enter a sequence, the calculator also reports:
- Primer length (nt)
- GC percentage
- Approximate Tm using the Wallace rule: Tm = 2(A+T) + 4(G+C)
This estimate is useful for a fast sanity check, but final annealing conditions should still be optimized experimentally.
Tips for better PCR primer performance
- Typical primer length: 18-25 bases.
- Avoid strong self-complementarity and 3' complementarity between primer pairs.
- Target GC content near 40-60% when possible.
- Keep amplicon and polymerase protocol in mind when choosing annealing temperature.
FAQ
Can I use TE buffer instead of water?
Yes. Many labs use low-EDTA TE for long-term primer stability. For some sensitive reactions, nuclease-free water may be preferred for working dilutions.
What if my working concentration is higher than my stock?
That is not possible by dilution. You must prepare a higher stock concentration first or change your target working concentration.
Is this an official NEB tool?
No. This is an independent educational calculator designed for common molecular biology workflows.