Ligation Calculator

Calculate how much insert DNA to add for a chosen insert:vector ratio.

How the Math Works

The Ligation Calculator uses a precise mathematical formula to determine the exact mass of insert DNA needed for successful ligation reactions. The calculation insert ng = ratio × (insert bp ÷ vector bp) × vector ng works by first comparing the size relationship between your insert and vector DNA fragments. By multiplying this size ratio by your desired molar ratio and the known vector mass, the formula calculates the optimal insert mass that ensures proper molar equivalence in your ligation mixture.

Practical Applications

To use this calculator in the laboratory, first measure your vector DNA concentration and determine its exact length in base pairs using gel electrophoresis or a DNA ladder. Next, decide on your target molar ratio (typically 1:1 or 3:1 insert-to-vector). Input these values along with your vector's mass in nanograms, and the calculator instantly provides the exact insert mass needed. This eliminates guesswork when setting up ligation reactions for plasmid construction or Gibson assemblies.

Day-to-Day Use

This calculator transforms frustrating molecular biology experiments by ensuring your ligation reactions succeed on the first attempt. Instead of running multiple trials with estimated insert amounts, you can precisely calculate the required DNA mass, saving hours of optimization time in the lab. Whether you're cloning a gene into a plasmid vector or assembling multiple DNA fragments, this tool provides the confidence that your ligation will work correctly, leading to more reliable experimental results and fewer repeat experiments.

Worked example

50 ng vector (5 kb), 1 kb insert, 3:1 → 30 ng insert.

FAQ