MAXScanner biology & lab calculator
DNA Ligation Calculator — Insert:Vector Molar Ratio, ng, fmol & Pipetting Volumes
Calculate required insert DNA mass from vector and insert lengths, compare the actual insert:vector molar ratio, convert both fragments to femtomoles and optionally calculate pipetting volumes from stock concentrations.
Results
Enter positive vector length, insert length, vector mass and target ratio
Formula, example and assumptions
target insert ng=vector ng×(insert bp/vector bp)×target ratio; dsDNA fmol=ng×10⁶/(bp×660).
With 50 ng of a 3,000 bp vector and a 1,000 bp insert, a 3:1 molar target requires 50 ng insert.
- The mass-ratio equation assumes both fragments are double-stranded DNA.
- A useful molar ratio depends on assembly chemistry, end type, fragment design and protocol; the calculator reports arithmetic rather than prescribing a laboratory condition.
Frequently asked questions
Why use a molar ratio instead of equal DNA mass?
Ligation joins molecules. Short fragments contain more molecules than long fragments at the same mass, so fragment length must be included.
Can this calculate pipetting volumes?
Yes. Enter vector and insert stock concentrations to convert the calculated nanogram amounts into microlitres.