What formula does the calculator use?

It uses nM = (µg/mL × 10⁶) ÷ (Da per bp or nt × DNA length).

What mass value is used for dsDNA?

The calculator uses an average molecular mass of 650 Da per base pair.

What mass value is used for ssDNA?

The calculator uses an average molecular mass of 330 Da per nucleotide.

Is 1 µg/mL equal to 1 ng/µL?

Yes. These concentration units are numerically identical.

What happens if I leave sample volume at zero?

The calculator skips the total-pmol calculation while still reporting concentration-based results.

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DNA Molar Concentration Calculator (µg/mL → nM)

Mass-to-molar DNA conversion: nM = (µg/mL × 10⁶)/(Da-per-bp × bp) with 650 Da/bp dsDNA and 330 Da/nt ssDNA, plus µM, pmol/µL, total pmol, and molecules/µL via Avogadro. Warns about the µM-vs-nM 1000× slip. NEB NEBioCalculator / Promega BioMath derived. Educational use only.

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2 examples

1000 bp fragment at 50 µg/mL → 76.923 nM

A 1000 bp double-stranded PCR fragment quantified at 50 µg/mL (= 50 ng/µL) has MW = 650 × 1000 = 650000 g/mol, so nM = 50 × 10⁶ / 650000 = 76.923 nM (0.077 µM, 0.077 pmol/µL). The whole 100 µL sample therefore holds 7.692 pmol ≈ 4.63 × 10¹² molecules — exactly the molar figure a ligation or assembly reaction needs.

{"result":"dsDNA 76.923 nM (0.077 µM, 0.077 pmol/µL); 100 µL holds 7.692 pmol total.","metadata":{"input":{"concentration":50,"dnaType":"dsDNA","lengthBp":1000,"sampleVolumeUl":100},"result":{"daltonsPerBp":650,"nanomolar":76.923,"micromolar":0.077,"pmolPerUl":0.077,"totalPmol":7.692}}}

76-nt ssDNA primer-scale prep at 20 µg/mL → 797.45 nM

A single-stranded 76-nt prep (M13 sequencing-primer scale) at 20 µg/mL switches the per-nucleotide mass to 330 Da: nM = 20 × 10⁶ / (330 × 76) = 797.45 nM. The example demonstrates the ssDNA constant swap and that the same algebra with 10⁻³ would wrongly report 0.797 µM as if it were nM.

{"result":"ssDNA 797.45 nM (0.8 µM, 0.8 pmol/µL).","metadata":{"input":{"concentration":20,"dnaType":"ssDNA","lengthBp":76,"sampleVolumeUl":0},"result":{"daltonsPerBp":330,"nanomolar":797.45,"micromolar":0.8,"pmolPerUl":0.8,"totalPmol":null}}}

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5 options

SettingsAdjust formats, ranges, numbers, and modes.5

DNA Concentration (µg/mL = ng/µL)numberRequiredMass concentration of the DNA sample. 1 µg/mL is numerically identical to 1 ng/µL.DNA TypeselectRequireddsDNA averages 650 Da/bp; ssDNA averages 330 Da/nt (NEB convention).DNA Length (bp)numberRequiredFull length of the DNA molecule in base pairs (nt for ssDNA).Sample Volume (µL, optional)numberOptionalVolume of the sample in µL; enter 0 to skip the total-pmol calculation.Decimal PlacesnumberOptional

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DNA Molar Concentration Calculator (µg/mL → nM)

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Examples

1. 1000 bp dsDNA fragment at 50 µg/mL

2. 76-nt ssDNA preparation at 20 µg/mL

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