idt dilution calculator

How to use this IDT dilution calculator

IDT oligos are commonly delivered lyophilized (dry), and the datasheet usually reports your yield in nmol. In day-to-day lab work, most protocols ask for concentration in µM. This calculator bridges that gap in seconds so you can move from tube label to pipette-ready volume without manual math.

The tool has two functions:

• Reconstitution calculation: how much water/TE to add to a dried oligo to reach a target stock concentration.
• Working dilution calculation: how much of your stock to mix with diluent to make a lower concentration for PCR, qPCR, cloning, CRISPR, or sequencing prep.

Core dilution formulas

Reconstitution from nmol

Because 1 nmol = 1000 pmol and 1 µM = 1 pmol/µL, the volume equation is straightforward:

Volume (µL) = (nmol × 1000) / target µM

Example: If IDT reports 25 nmol and you want a 100 µM stock, add 250 µL buffer.

Working dilution from stock

Use the classic dilution equation:

C1 × V1 = C2 × V2

• C1 = stock concentration
• V1 = volume of stock to pipette
• C2 = desired working concentration
• V2 = final volume needed

Then calculate diluent as V2 - V1.

Practical concentration choices for IDT oligos

Different labs use different defaults, but these are common:

• 100 µM stock for long-term freezer storage and flexibility.
• 10 µM working solution for routine PCR primers.
• 1–5 µM for some probe applications or sensitive assays requiring finer handling.

If the calculated pipetting volume is very small (for example < 2 µL), make an intermediate dilution first to reduce pipetting error.

Step-by-step workflow in the lab

1. Read your oligo documentation carefully

Confirm the delivered amount in nmol from the IDT label or certificate. Avoid mixing up “ordered scale” with “actual recovered amount.”

2. Pick your stock concentration

Choose a concentration that matches your workflow. Most molecular biology pipelines are comfortable with a 100 µM stock.

3. Reconstitute with nuclease-free diluent

Use nuclease-free water or low-EDTA TE, depending on your downstream assay needs. Mix gently and allow complete dissolution.

4. Build a working solution

Prepare 10 µM (or other desired) aliquots from your stock so you avoid repeated freeze-thaw cycles of the master stock tube.

5. Label and store correctly

Include oligo name, concentration, date, and initials. Store aliquots at recommended temperatures and track usage in your lab notebook/LIMS.

Common mistakes and how to avoid them

• Unit confusion: Keep nmol, pmol, µL, and µM straight on paper before pipetting.
• Ignoring existing volume: If you already added liquid, calculate whether you should add more or remake the sample.
• Pipetting tiny volumes: Use intermediate dilutions for better accuracy.
• Over-thawing stocks: Aliquot early to preserve oligo quality and consistency.
• No verification: For critical work, verify concentration with UV absorbance when appropriate.

Quick example scenarios

Scenario A: Reconstitution

You received 18 nmol and want 200 µM stock.

Volume = (18 × 1000) / 200 = 90 µL. Add 90 µL buffer.

Scenario B: Working dilution

You have 100 µM stock and need 500 µL of 10 µM working solution.

V1 = (10 × 500) / 100 = 50 µL stock. Add 450 µL diluent.

Final notes

This calculator is intended for planning and routine lab preparation. Always follow your institutional SOPs, assay kit instructions, and quality standards for regulated environments. For high-stakes experiments, include controls and independent concentration checks.