Formula Used
The calculator first converts the primer quantity into picomoles. One nanomole equals 1000 picomoles. Since micromolar equals picomoles per microliter, the stock volume is simple.
Stock volume, µL = primer amount, pmol ÷ desired stock concentration, µM
For the working tube, the calculator uses the dilution equation.
C1 × V1 = C2 × V2
Stock volume for working tube = target working concentration × final working volume ÷ stock concentration
Diluent volume = final working volume − stock volume added
If mass is entered, molecular weight is used. The relation is ng = nmol × molecular weight.
How to Use This Calculator
- Enter the primer name from your tube label or order sheet.
- Enter the supplied amount in nmol, pmol, ng, or µg.
- Add molecular weight only when using a mass unit.
- Choose the stock concentration required by your lab.
- Enter the working concentration used in your assay.
- Add planned reactions, primer volume per reaction, and overage.
- Press the calculate button and review the result above the form.
- Download the CSV or PDF for lab records.
Example Data Table
| Primer |
Amount |
Stock µM |
Stock Volume |
Working µM |
Working Volume |
Stock Added |
Diluent Added |
| Forward Primer A |
25 nmol |
100 |
250 µL |
10 |
500 µL |
50 µL |
450 µL |
| Reverse Primer B |
50 nmol |
100 |
500 µL |
10 |
1000 µL |
100 µL |
900 µL |
| Probe Control C |
10 nmol |
50 |
200 µL |
5 |
250 µL |
25 µL |
225 µL |
Why Primer Dilution Matters
Primer dilution is a small step, yet it controls many later results. A primer that is too strong can raise nonspecific bands. A primer that is too weak can lower yield. Clear dilution math also prevents wasted oligo material. This calculator follows common IDT style values, where oligo amount is often supplied in nanomoles. It turns that amount into a stock volume, then plans a working tube for routine reactions.
Stock Solution Planning
A stock tube is the concentrated primer reserve. Many labs prepare stocks at 100 micromolar. Other labs use 200 micromolar or 50 micromolar, based on storage rules and assay needs. The calculator uses the amount of primer and the desired stock concentration. Because micromolar equals picomoles per microliter, the conversion is direct. One nanomole equals one thousand picomoles. More amount needs more buffer. Higher stock strength needs less buffer.
Working Dilution Planning
A working primer is easier to pipette into reactions. Ten micromolar is common for PCR setup, but the best value depends on protocol design. The calculator applies the dilution equation C1V1 equals C2V2. It reports the stock volume to add, plus water or buffer volume. It also checks the pipetting volume. If the stock volume is tiny, prepare a larger working tube or reduce the stock concentration.
Reaction and Yield Checks
Advanced planning does more than calculate one tube. It estimates how many reactions the working dilution supports. It includes overage for pipetting loss. This helps when preparing a master mix. It also reports total primer mass when molecular weight is entered. That can help compare records from vendors, labels, and lab notebooks.
Good Lab Practice
Always spin the primer tube before opening it. Add the full resuspension volume to the dried pellet. Mix gently, then allow the tube to sit for several minutes. Vortex briefly if your lab permits it. Store concentrated stock in small aliquots. Keep freeze thaw cycles low. Label every tube with primer name, concentration, date, and buffer. Recalculate when units change. Review final volumes before pipetting. A careful dilution record saves time and protects experiments. Keep a second copy of the calculation with project notes, lot numbers, and assay conditions for later review and troubleshooting checks.
FAQs
1. What does this primer dilution calculator do?
It calculates stock resuspension volume, working dilution volume, remaining primer, reaction support, and pipetting checks from primer amount and target concentrations.
2. Why is µM used for primer concentration?
Primer protocols often use micromolar units because µM equals picomoles per microliter. This makes tube dilution and reaction setup easier to calculate.
3. What stock concentration should I choose?
Many labs use 100 µM primer stocks. Your protocol may use 50 µM or 200 µM. Follow your assay method and lab storage rules.
4. What working concentration is common for PCR primers?
A 10 µM working primer is common for many PCR workflows. Some assays require different strengths. Always follow the validated protocol for your experiment.
5. Why does the calculator ask for overage?
Overage covers pipetting loss and dead volume. It helps ensure enough working primer is available for every planned reaction.
6. When is molecular weight required?
Molecular weight is needed when the primer amount is entered as ng or µg. It converts mass into nmol for concentration calculations.
7. What should I do if stock volume is too small?
Increase the working dilution volume, reduce the stock concentration, or prepare an intermediate dilution. This improves pipetting accuracy.
8. Can I save the result?
Yes. Use the CSV button for spreadsheet records. Use the PDF button for a simple lab notebook copy.