BioinformaticsBrowser-sidedsDNA / ssDNAng/uL ↔ nM ↔ pmol

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.

Start CalculatingHow the Math Works
100% browser-sidedsDNA and ssDNAInstant recalculation
Quick reference
A concise summary of the conversion logic.
Molecular weight estimate
660 g/mol per unit
Use for double-stranded DNA fragments, PCR products, and plasmid inserts.
Mass to molarity
nM = ng/uL × 1,000,000 / MW
Molarity to pmol
pmol = nM × volume(uL) / 1,000
Calculator
Enter the sequence length and one known value. The calculator updates instantly in your browser.

Double-stranded DNA uses 660 g/mol per base pair.

Enter base pairs for dsDNA or nucleotides for ssDNA.

Enter the value you already know from your assay or measurement.

pmol uses the sample volume below to convert between amount and concentration.

Used when converting nM to total pmol.

Preset examples
Measurement note

If you measured A260 first, convert that absorbance to ng/uL using your assay factor, then paste the mass concentration here. The calculator will handle the molar conversion and the total pmol estimate.

Live conversion
Updated in real time from the current inputs.
Estimated molecular weight
990,000 g/mol
1,500 bp × 660 g/mol
Molar concentration
12.63 nM
Converted from 12.5 ng/uL
Mass concentration
12.5 ng/uL
The mass concentration equivalent for this sequence.
Total amount
0.01 pmol
1 uL sample volume
Total DNA mass in sample
12.5 ng
Mass across the sample volume you entered.
Helpful reference: 1 nM of this sequence corresponds to 0.99 ng/uL.
What the math is doing
The formulas are simple, but the unit conversion is easy to mix up during lab work.

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.
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.
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.
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.

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FAQ

Answers to the most common questions about DNA unit conversion.