Plasmid Copy Number Calculator

Convert plasmid mass and size into copy number and molar concentration.

About Plasmid Copy Number Calculator

Double-stranded DNA averages about 650 grams per mole per base pair, so plasmid molar mass follows from its length. Converting mass to moles and multiplying by Avogadro's number gives absolute copy number. Absolute copy number is what quantitative PCR standards and transfection ratios depend on, and it cannot be read from concentration alone without the plasmid size.

Formula

Plasmid Copy Number

Copies = (mass ÷ (bp × 650 g/mol)) × Avogadro's number

650 g/mol: Average molar mass of one base pair of double-stranded DNA
Avogadro's number: 6.022 × 10²³ molecules per mole

Worked example

With the default values below, Plasmid Copy Number Calculator returns Plasmid Copies of 92,646,153,846. Change any input above and every figure here is recalculated in your browser.

Inputs used

Plasmid massminimum 0.001 ng: 500 ng
Plasmid sizeminimum 1 bp: 5,000 bp
Sample volumeminimum 0.1 uL: 50 uL

Results

Plasmid Copies: 92,646,153,846
Molar Mass: 3,250,000 g/mol
Concentration: 10.000 ng/uL
Molar Concentration: 3.0769 nM
Copies per Microlitre: 1,852,923,077

Step by step

1Values used
2Plasmid Copy Number
3Plasmid Copies= 92,646,153,846
4Molar Mass= 3,250,000 g/mol
5Concentration= 10.000 ng/uL
6Molar Concentration= 3.0769 nM
7Copies per Microlitre= 1,852,923,077

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Plasmid Copy Number calculated?

Copies = (mass ÷ (bp × 650 g/mol)) × Avogadro's number Double-stranded DNA averages about 650 grams per mole per base pair, so plasmid molar mass follows from its length. Converting mass to moles and multiplying by Avogadro's number gives absolute copy number.

Why does Plasmid Copy Number matter?

Absolute copy number is what quantitative PCR standards and transfection ratios depend on, and it cannot be read from concentration alone without the plasmid size.

What values do I need to enter?

This calculator takes 3 inputs: Plasmid mass, Plasmid size, Sample volume. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.