DNA Concentration Calculator
Convert DNA concentration between ng/uL, nM, and pmol from a sequence length. Built for quick lab checks on PCR products, inserts, oligos, and other sequence workflows.
- 100% browser-side
- dsDNA and ssDNA
- Instant recalculation
1Describe the DNA
DNA type
Double-stranded DNA uses 660 g/mol per base pair. Use for double-stranded DNA fragments, PCR products, and plasmid inserts.
Used to estimate molecular weight unless an exact value is supplied.
Estimated molecular weight
990,000 g/mol
1,500 bp × 660 g/mol per bp
Preset examples
2Type the value you have into any box
The other boxes are calculated from it. Molecular weight links mass and moles; the sample volume links a concentration to a total.
Per µL
Concentration
In the tube
Needed only to connect a concentration with a total amount.
12.5 ng/µL of 1,500 bp dsDNA =
12.63 nM
What the math is doing
The formulas are simple, but the unit conversion is easy to mix up during lab work.
- 1MW = 1,500 bp × 660 g/mol = 990,000 g/mol
- 2nM = 12.5 ng/µL × 1,000,000 ÷ 990,000 g/mol = 12.63 nM
- 3ng = 12.5 ng/µL × 1 µL = 12.5 ng
- 4pmol = 12.63 nM × 1 µL ÷ 1,000 = 0.01263 pmol
- 5copies/µL = 12.63 nM × 6.022 × 108 = 7.604 × 109
First the calculator estimates the molecular weight from the sequence length. Then it converts between mass concentration and molarity using the average molecular weight for dsDNA or ssDNA.
If you need total pmol, the calculator multiplies the concentration by the sample volume. That keeps concentration and amount separate instead of assuming they mean the same thing.
How this works
A small set of assumptions is enough for most routine sequence QC, cloning prep, and sample normalization work.
1. Estimate molecular weight
Multiply the sequence length by 660 g/mol for dsDNA or 330 g/mol for ssDNA. This is the standard quick estimate used in the lab.
Molecular weight estimate
MW = length × 660 g/mol (dsDNA) or × 330 g/mol (ssDNA)
2. Convert to molarity
Use the molecular weight to turn ng/uL into nM, or reverse the same relationship if you already know the molar concentration.
Mass to molarity
nM = ng/uL × 1,000,000 / MW
3. Compute total pmol
Multiply nM by the sample volume to get the total amount in pmol. This is the most useful value when planning ligations or mixes.
Molarity to pmol
pmol = nM × volume(uL) / 1,000
When to use this page
Use it when you have a sequence length and one measurement already in hand, and you need the other common DNA units for a protocol, notebook, or QC sheet.
It is a good fit for sequencing prep, cloning, oligo handling, and quick bench-side decisions where you do not need a heavier lab calculation suite.
Runcell bridge
If you are documenting sequencing, cloning, or assay prep, keep the calculation close to your notes and analysis workflow so the numbers stay connected to the rest of the project.
Related tools
Sequence calculations usually sit next to other small bioinformatics tasks.
FAQ
Answers to the most common questions about DNA unit conversion.
What does this calculator assume for dsDNA and ssDNA?
It uses the standard average molecular weight approximation of 660 g/mol per base pair for dsDNA and 330 g/mol per nucleotide for ssDNA. That is accurate enough for quick lab planning and routine sequence QC.
Why does pmol need a sample volume?
pmol is an amount, not a concentration. To convert between nM and total pmol, the calculator needs the sample volume in microliters. If you only care about concentration, set the volume to the amount you are working with.
Can I use A260 readings here?
Yes, but first convert the A260 measurement into ng/uL using your instrument or assay factor. Then paste that mass concentration into the calculator to get nM and pmol.
Is this exact for every sequence?
No. The calculator uses average molecular weights, so it is an estimate. For short oligos or vendor-verified constructs, the exact molecular weight can differ slightly because base composition changes the result.
When should I use the ssDNA mode?
Use ssDNA mode for single-stranded oligos, primers, and other single-stranded sequences. For PCR products, inserts, and plasmid fragments, dsDNA is usually the right choice.
Is my sequence data sent anywhere?
No. All calculations run entirely in your browser. Nothing is uploaded to Runcell to perform the conversion.