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Molecular biology Cloning

Ligation molar ratio calculator (vector:insert)

Calculate required insert mass (ng) from vector mass and length plus a target molar ratio (e.g., 1:3). If concentration is known, required volume (µL) is also shown.

All calculations run in your browser. No data is sent.

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How to use (3 steps)

  1. Select an example or enter vector length (bp) and insert length (bp).
  2. Enter the target molar ratio (e.g., 1:3) and vector mass (ng).
  3. The required insert mass (ng) and volume (µL) are shown (if concentration is provided).

This is a quantity calculator. Optimal ratios depend on end type and conditions; follow your protocol.

Inputs (vector/insert)

—

Custom ratio
Concentrations (optional: enables required volume in µL)
Advanced settings

For dsDNA, the default guide uses 660 g/mol/bp. In insert mass calculation the factor largely cancels, so the result is driven mainly by bp ratio and mass.

Results

Required insert amount
— ng
Required insert volume (if concentration is provided)
— µL
Required vector volume (if concentration is provided)
— µL
Moles (guide)
—
Actual ratio (insert/vector)
—
Vector
— ng
Insert
— ng
The share URL can restore your inputs (fixed English keys).
Compare common ratios (optional)
Ratio (vector:insert) Insert amount (ng) Insert volume (µL)

This tool calculates amounts only. It does not guarantee success.

How it’s calculated

  1. As a dsDNA approximation, pmol = (mass_ng × 1000) / (bp × 660).
  2. Compute vector pmol from vector mass and length.
  3. Insert target pmol = vector pmol × target ratio, then convert back to mass (ng).
  4. If concentration is known, volume = mass / concentration.

Values are guides. Follow your protocol for final conditions.

FAQ

Why use molar ratios?
Fragments of different lengths have different molecule counts at the same mass. Molar ratios keep molecule counts consistent.
What ratios are commonly used?
Vector:insert ratios like 1:3 or 1:5 are common starting points. Optimal ratios depend on ends and conditions.
Which vector length should I use?
Use the actual length of the linearized vector fragment used for ligation, often the full plasmid length.
I do not know the insert concentration.
You can still calculate required mass (ng). Volume (µL) is shown only when concentration is provided.
My volumes are extremely small (e.g., 0.1 µL).
Very small volumes are error-prone. Consider intermediate dilution or adjust vector mass and reaction volume.
Will these amounts guarantee success?
No. This tool calculates amounts only. Success depends on end type, reaction conditions, and DNA quality.