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.

Used to estimate molecular weight unless an exact value is supplied.

A supplied molecular weight overrides the length-based average.

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

Concentrations and total amounts are calculated as distinct quantities.

Needed only to connect a concentration with a total amount.

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.
Primary conversion · Molar concentration
12.6263 nM
Converted from the entered ng/µL value.
Estimated molecular weight
990,000 g/mol
660 g/mol per bp average.
Mass concentration
12.5 ng/µL
Mass per sample volume.
Total DNA mass
12.5 ng
Total mass across the sample.
Total molar amount
0.0126263 pmol
Total amount of DNA molecules.
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.

Explore bioinformatics toolsOpen notebook workflows

Related tools

Sequence calculations usually sit next to other small bioinformatics tasks.

Reverse Complement

Generate the reverse complement of a DNA sequence

Open tool
GC Content Calculator

Measure GC percentage for a sequence

Open tool
Protein Concentration Calculator

Estimate protein concentration and molarity

Open tool
Restriction Site Finder

Locate common restriction enzyme cut sites

Open tool

FAQ

Answers to the most common questions about DNA unit conversion.