Resuspension Calculator
Use this resuspension calculator to work out the buffer volume for a lyophilized oligo, primer or peptide. Enter the mass, molecular weight, and the concentration you want (µM) — it returns the volume of water or buffer to add.
Enter mass, molecular weight, and the concentration you want to get the buffer volume to add.
How to resuspend a lyophilized sample
Resuspension is just making a solution at a known concentration from a dry amount. First convert the mass to moles, then divide by the target molarity:
Equivalently, if you already know the amount in nmol, the volume is nmol ÷ µM × 1000. The molecular weight is in g/mol (Daltons) and should come from your vendor spec sheet.
Worked example
A primer of 100 µg with MW 6600 g/mol to reach 100 µM: volume = 100 × 1,000,000 ÷ (6600 × 100) ≈ 151.5 µL of buffer (that is about 15.15 nmol).
Typical target concentrations by application
The right target µM depends entirely on what the oligo is for — these are the concentrations most protocols call for:
| Application | Typical target |
|---|---|
| PCR primer stock | 100 µM |
| PCR / qPCR working dilution | 10 µM |
| Sanger sequencing primer | 3.2 µM |
| siRNA stock | 20–100 µM |
| gBlock / synthetic DNA fragment | 10–20 ng/µL (convert via MW first) |
Related tools
To go from mg/mL to molarity, use the mg/mL ⇆ molarity calculator. To then dilute the stock down, use the dilution calculator.
Frequently asked questions
›How do I resuspend a lyophilized oligo to 100 µM?
Convert the amount to nmol, then divide by the target µM and multiply by 1000. For a mass in µg, nmol = mass ÷ MW × 1000, so the volume in µL is (mass × 1,000,000) ÷ (MW × target µM). Add that many µL of buffer or nuclease-free water.
›What is the resuspension formula?
Volume (µL) = mass (µg) × 1,000,000 ÷ (molecular weight × target concentration in µM). Equivalently, µL = nmol ÷ µM × 1000. It gives the buffer volume to reach the concentration you want.
›What molecular weight should I use for an oligo?
Use the exact MW from your synthesis or spec sheet (in g/mol / Daltons). A rough estimate for single-stranded DNA is length × 330 g/mol per base, but the vendor value is more accurate, especially with modifications.
›Water or buffer for resuspension?
TE buffer (10 mM Tris, 1 mM EDTA) is common for long-term storage because EDTA chelates nucleases; nuclease-free water is fine for short-term use. This calculator only gives the volume — the diluent choice is yours.
›What concentration should I resuspend a primer to?
Most vendors ship oligos sized for a 100 µM stock — resuspend to that first, store frozen, then dilute a small amount to a 10 µM working stock for PCR/qPCR so you avoid repeated freeze-thaw of the concentrated stock.
Related calculators
Solve C₁V₁ = C₂V₂ for any unknown — stock concentration, volume, or final concentration.
Find molarity from mass and molecular weight, or the mass needed for a target molarity.
Convert between moles, volume, and molar concentration (mol/L) in any direction.
Dilute a solution with C₁V₁ = C₂V₂ — solve for stock volume, final concentration or volume.
Find the concentration after dilution from stock concentration, stock volume and final volume.
Dilute a stock solution to a target concentration with full unit switching.