Ligation Calculator

Use this calculator to set up a sticky- or blunt-end cloning ligation when you know the vector length and mass, the insert length, and how many insert molecules you want per vector molecule (often 3:1).

The calculation is: insert mass (ng) = (insert bp ÷ vector bp) × vector mass (ng) × insert-to-vector molar ratio. Lengths are in base pairs and masses are in nanograms. The formula assumes the same average mass per base pair for vector and insert.

This is a molar-ratio setup, not a guarantee of colony count. Enzyme quality, ends, and DNA purity still matter.

Vector length (bp): Length of the vector or backbone in base pairs.

Vector mass (ng): How much vector DNA you are putting in the tube, in nanograms.

Insert length (bp): Length of the insert in base pairs.

Insert:vector molar ratio: Insert molecules per vector molecule. 3 means a 3:1 ligation.

Insert mass (ng): Nanograms of insert DNA to add to that vector amount.