Convert plasmid mass and size into copy number and molar concentration.
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.
Plasmid Copy Number
Copies = (mass ÷ (bp × 650 g/mol)) × Avogadro's number
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.
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.
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.