What this calculator does
Lyophilised (freeze-dried) reagents, from antibodies to synthesised oligonucleotides, are shipped and stored as a dried mass and need to be dissolved in a specific volume of buffer to reach a usable working concentration. Getting that volume right the first time avoids wasting precious material on a second dilution or concentration step.
The relationship is the same C₁V₁ = C₂V₂ logic used throughout dilution calculations, just applied from a starting point of total amount rather than a starting concentration: the mass of dried material divided by the volume of buffer added gives the resulting concentration, and the calculation runs in either direction depending on which figure is already known.
The formula
To find the volume needed for a target concentration, divide the amount of dried material by that target concentration. To find the concentration a given volume of buffer will produce, divide the amount of dried material by that volume instead.
| Term | Meaning |
|---|---|
| Amount | The total mass of dried or lyophilised material in the vial, as stated on the product label or spec sheet. |
| Target concentration | The working concentration wanted once the material is dissolved. |
| Resulting concentration | The concentration actually produced by adding a specific volume of buffer, when that volume is fixed rather than the concentration. |
The inputs explained
| Field | What to enter |
|---|---|
| Amount of dried material (µg) | The total amount of dried material in the vial, from the product label or certificate of analysis. |
| Solve for | Choose from Volume needed (known target concentration), Resulting concentration (known volume added). |
| Known value (target concentration in µg/µL if solving volume; volume added in µL if solving concentration) | Enter the target concentration if solving for volume, or the volume of buffer you plan to add if solving for the resulting concentration. |
When to use it
Resuspending a lyophilised antibody or protein
Product data sheets typically state a target working concentration; this calculator turns that target and the vial's stated mass into the exact buffer volume to add.
Resuspending a synthesised oligonucleotide
Oligo vendors report the total nanomoles or micrograms synthesised, and a target concentration (often in µM) determines how much buffer or water to add to reach a convenient stock concentration.
Working backwards from an available buffer volume
When only a fixed volume of buffer is on hand, solving for the resulting concentration instead shows what stock strength that volume will actually produce.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much buffer to add for different target concentrations
A fixed 100 µg vial, resuspended to a range of target concentrations.
| Target concentration | Buffer volume to add |
|---|---|
| 0.1 µg/µL | 1,000.000 µL |
| 0.5 µg/µL | 200.000 µL |
| 1 µg/µL | 100.000 µL |
| 2 µg/µL | 50.000 µL |
| 5 µg/µL | 20.000 µL |
| 10 µg/µL | 10.000 µL |
Questions
What happens if I add the wrong volume of buffer?
The resulting concentration will be higher or lower than intended, in inverse proportion to the volume used; adding half the calculated volume doubles the concentration, and adding double the volume halves it.
Does resuspension volume depend on the molecule's molar mass?
Only if the target concentration is expressed in molar terms (such as µM) rather than mass terms (such as µg/µL). This calculator works directly in mass-based units; converting a molar target to a mass-based one first requires the molar mass of the specific substance.
Can I use this for reconstituting more than just antibodies or oligos?
Yes, the same mass-over-volume relationship applies to any dried or lyophilised material being dissolved to a target concentration, including enzymes, standards and other lab reagents supplied in dried form.
Why does the calculator ask me to choose what to solve for?
Depending on the situation, either the target concentration or the available buffer volume is the fixed, known quantity; selecting which one you already know tells the calculator which variable to solve for instead.
For the same underlying dilution relationship applied to liquid stock solutions, see the solution dilution calculator. For preparing a target molarity directly from a solid mass, see the molarity calculator.