How this calculator works
Molecule count depends on mass divided by fragment length. Multiplying vector mass by the length ratio and desired molecule ratio gives insert mass. Enter lengths in base pairs, converting kilobases by multiplying by 1,000. The result plans DNA quantities, not ligase, buffer or reaction volume. Fragment ends and protocol chemistry still matter.
Formula
Insert mass = molar ratio × vector mass × insert bp / vector bp. Molar ratio = (insert mass / insert bp) / (vector mass / vector bp). Each inverse mode rearranges the same relation.
Worked example
For 50 ng of a 3,000 bp vector and a 1,000 bp insert at 3:1, use 50 ng insert. For a 500 bp insert, a 3,000 bp vector at 100 ng and a 1:1 ratio, use 16.6667 ng insert.
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Frequently asked questions
Is a 3:1 ratio the same as three times the vector mass?
Only if insert and vector lengths are equal. For shorter inserts, fewer nanograms supply the same number of molecules.
Which ratio should I use?
Use the ratio in your ligation protocol. Three inserts per vector is a common starting point, but fragment ends and cloning design can change the choice.
Can I enter micrograms?
The fields explicitly use nanograms. Multiply a mass in micrograms by 1,000 before entering it.