neb oligo calculator

What this NEB oligo calculator helps you do

When you receive lyophilized oligos, the first challenge is practical: how much buffer or water should you add to hit a useful stock concentration? Then comes dilution math, annealing setup, and quick sequence checks before you run experiments. This page puts those common calculations in one place so you can move faster at the bench.

Even if you use official vendor tools, it is still valuable to understand the underlying formulas. That way, you can sanity-check your numbers, catch unit mix-ups, and adapt to custom protocols for cloning, PCR, CRISPR guides, or adapter assembly.

Core formulas used in oligo prep

Reconstitution from nmol to µM

For most lab work, µM is convenient because 1 µM = 1 pmol/µL. If you receive an oligo amount in nmol, convert nmol to pmol by multiplying by 1000. The volume needed is:

• Volume (µL) = (Amount in nmol × 1000) / Desired concentration (µM)

Dilution with C1V1 = C2V2

To make a working tube from a concentrated stock:

• V1 = (C2 × V2) / C1
• V1 is stock volume, and water/buffer is V2 − V1

Quick sequence properties

The calculator returns length, base composition, GC%, and an estimated melting temperature (Tm). For a fast estimate we use:

• Wallace rule: Tm ≈ 2°C × (A+T) + 4°C × (G+C)
• Long-oligo approximation: Tm ≈ 64.9 + 41 × (G+C−16.4)/N

These are screening-level estimates. Final assay design should use nearest-neighbor thermodynamics and your actual salt/additive conditions.

Example workflow in the lab

Step 1: Make a 100 µM stock

If your tube says 25 nmol, adding 250 µL gives you a 100 µM stock. This is a common “master stock” concentration that stores well and is easy to dilute.

Step 2: Prepare a 10 µM working dilution

From 100 µM stock, to make 200 µL at 10 µM:

• V1 = (10 × 200)/100 = 20 µL stock
• Add 180 µL nuclease-free water or TE buffer

Step 3: Anneal complementary oligos

If both forward and reverse stocks are 100 µM and you want 100 µL of 10 µM duplex, add 10 µL of each oligo and 80 µL diluent. Then heat and cool according to your protocol.

Common mistakes this prevents

• Confusing nmol, pmol, and µM units
• Using C1V1 = C2V2 with swapped concentrations
• Forgetting that duplex concentration depends on limiting strand
• Skipping sequence QA and missing incorrect characters in copied sequences

Practical notes

Store concentrated stocks at low temperature and avoid repeated freeze-thaw cycles by making aliquots. For sensitive applications, track whether you are resuspending in water vs TE and whether EDTA in TE affects downstream enzymatic steps.

This calculator is designed for quick bench math and educational use. Always verify critical concentrations and sequence-dependent behavior against your exact NEB protocol, oligo chemistry, and assay conditions.