Use this free online DNA ligation calculator to determine the insert DNA mass required for a vector-insert ligation from vector mass, vector length, insert length, and target molar ratio.
Useful Checks
Use Primer Designer when cloning primers need restriction sites or overhangs before calculating ligation amounts.
Use Restriction Site Analyzer first to confirm enzyme sites and fragment sizes, then use this calculator for insert-to-vector molar ratio setup.
Minimum Inputs Needed
Vector length.
Insert length.
Vector DNA amount.
Insert:vector molar ratio.
Optional Settings
Vector / insert length units
Use bp or kb, depending on how your fragment size is written.
Custom insert:vector ratio
Use this if your protocol uses a ratio that is not in the preset list.
Reaction volume, µL (optional)
Enter this if you also want concentration estimates for the ligation mix.
How To Use
Enter vector length.
Enter insert length.
Enter how much vector DNA you will use.
Choose the insert:vector ratio.
Click Calculate insert amount.
Understanding The Results
The main result is the insert DNA mass to add.
The formula is: insert mass = vector mass × insert length / vector length × insert:vector molar ratio.
The detailed result also reports vector and insert femtomoles, total DNA mass, and a comparison table for common molar ratios.
If reaction volume is entered, vector, insert, and total DNA concentration estimates are shown.
Copy result copies the full ligation setup for notes or protocols.
Accepted Input Formats
Lengths can be bp or kb.
Vector DNA amount is in ng.
Reaction volume is in µL.
Assumptions And Limitations
The calculation does not account for DNA purity, end compatibility, ligase type, or reaction efficiency.
Use it as an initial planning estimate and adjust based on your protocol.
Example
For a 3000 bp vector, 1000 bp insert, 50 ng vector, and 3:1 ratio, add 50 ng insert.
Use note: These tools are for research and educational planning. Check important calculations and sequence designs before ordering reagents or running experiments.