Biology

Ligation Calculator (Insert to Vector Molar Ratio)

Enter vector amount, both lengths and the molar ratio to get the insert mass.

By TheCalcTools Updated October 17, 2026 Formula checked and tested

Your numbers

Vector DNA (ng)

Vector length (bp)

Insert length (bp)

Insert : vector molar ratio

Insert DNA needed (ng)

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Vector (fmol)

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Insert (fmol)

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Ligation efficiency depends on the number of molecules, not their mass. Insert mass = vector mass × (insert length ÷ vector length) × molar ratio.

Ratios of 3:1 are typical for standard cloning; small inserts often use 5:1 or more.

ng insert = ng vector × (bp insert ÷ bp vector) × ratio

Using the default values shown in the calculator:

Result:

Which ratio should I use?

Start with 3:1 for most inserts. For blunt ends or small inserts try 5:1 to 10:1; check your ligase’s protocol.