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Oligo Resuspension Calculator

Ready to calculate
V = n / C.
7 Amount + 9 Conc Units.
Pipetting Class Check.
100% Free.
No Data Stored.

How it Works

01Read Oligo Amount (n)

From your synthesis report (IDT, Sigma, Thermo) — typical scales 100 nmol, 250 nmol, 1 μmol

02Pick Target Concentration (C)

100 μM is the universal default for primer/oligo stocks (dilute 100× into PCR for 1 μM working)

03Apply V = n / C

Volume of buffer to add = moles divided by molar concentration. Result in liters, auto-displayed in μL/mL

04Pipette + Vortex

Add the buffer (TE or nuclease-free water), vortex briefly, let stand 5-10 min, centrifuge to collect

What is a Resuspension Calculator?

Every molecular biologist faces the same calculation every Monday morning: a fresh tube of lyophilized DNA oligo arrives from IDT, Sigma, or Thermo Fisher, marked "100 nmol synthesis scale" — how much buffer do you add to make a usable stock solution? The answer is the elegantly simple Resuspension formula V = n / C, where V is the volume of buffer to add, n is the moles of dry material in the tube (from the synthesis report), and C is the target stock concentration. Our Resuspension Calculator implements this universal formula with full unit flexibility — 7 amount units (mol, mmol, μmol, nmol, pmol, fmol, amol) covering every commercial synthesis scale, 9 concentration units (M, mM, μM, nM, pM, fM, aM, zM, yM) covering every conceivable working dilution, and 5 output volume units that auto-pick the most readable display (μL for typical 1-1000 μL preps; mL for larger preps; L for industrial scale).

The standard recipe — 100 nmol oligo + 1 mL buffer = 100 μM stock — is the universal default at every commercial DNA synthesis vendor. It gives you a 100× concentrate for typical 1 μM working PCR primers, dilutable on demand into reactions. Just enter the oligo amount from your synthesis report and the desired final concentration, and the calculator instantly returns the buffer volume to add, classified into 5 pipetting bands: too-small (< 1 μL — impractical to pipette accurately, suggests reducing target concentration); tight (1-50 μL — requires careful P10/P20 work); good (50 μL - 5 mL — practical with standard pipettes); large (5-100 mL — serological pipettes); huge (> 100 mL — usually means inputs are wrong).

Designed for molecular biology students learning oligo handling protocols, PCR primer designers preparing fresh primer stocks, CRISPR-Cas9 researchers resuspending guide RNAs, siRNA users for gene-knockdown experiments, plasmid engineers handling synthesized DNA fragments, and protein chemists for lyophilized peptide and protein resuspension, the tool runs entirely in your browser — no data is stored or transmitted.

Pro Tip: Pair this with our Molarity Calculator for converting ng/μL to molarity (DNA concentration is often reported by mass), or our Solution Dilution Calculator for diluting your stock to working concentration via C₁V₁ = C₂V₂.

How to Use the Resuspension Calculator?

Read Oligo Amount (n) from Synthesis Report: Your DNA synthesis vendor (IDT, Sigma, Thermo, Eurofins) ships oligos with a printed yield in nmol. Common scales: 25 nmol (smallest), 100 nmol (standard primer order), 250 nmol, 1 μmol (large prep). The actual yield can be slightly less than the ordered scale — always use the actual yield printed on the tube.
Choose Target Concentration (C): Universal default for primer/oligo stocks: 100 μM. This gives a 100× concentrate that's easy to dilute to typical 1 μM working concentrations for PCR. Other common stocks: 1 mM (high-concentration master stocks), 10 μM (pre-diluted working stocks), 200 μM (very-high-conc for limited-volume reactions).
Apply V = n / C: Volume of buffer to add equals moles divided by molar concentration. Example: 100 nmol / 100 μM = 100×10⁻⁹ mol / 100×10⁻⁶ mol/L = 1×10⁻³ L = 1 mL. The famous IDT recipe.
Pick Buffer: TE buffer (10 mM Tris-HCl pH 8.0, 1 mM EDTA) for long-term DNA storage — the EDTA chelates divalent metals that activate trace nucleases. Nuclease-free water for short-term work or when EDTA would interfere with downstream applications. RNase-free water for RNA oligos. Never use unsterile water — even trace nucleases will degrade oligos.
Resuspend Properly: Add the calculated buffer volume to the dry pellet. Vortex briefly (2-3 seconds), let stand at room temperature for 5-10 minutes for complete dissolution, then briefly centrifuge to collect liquid at the tube bottom. Visible pellets should disappear entirely — if not, vortex more or warm to 37 °C briefly.
Read Pipetting Class: 5-band classification (too-small / tight / good / large / huge) tells you whether the calculated volume is practical. If your result is < 1 μL, reduce the target concentration; if > 100 mL, increase the target concentration to make a more practical stock.

How is the resuspension volume calculated?

The resuspension formula is the simplest of all colligative-property calculations — pure stoichiometry connecting moles, molar concentration, and volume. Mastering it is the first step in any molecular biology workflow. Here's the complete framework:

The formula derives directly from the definition of molar concentration: M = mol / L → L = mol / M → V = n / C. No special derivation needed; it's a direct rearrangement of the universal molarity definition.

The Master Formula

For any solute being dissolved to a target molar concentration:

V = n / C

where V is the volume of solvent (buffer) to add, n is the moles of solute being dissolved, and C is the target molar concentration. Result is in liters when n is in mol and C is in mol/L.

Worked Example: The IDT Standard Recipe

100 nmol of dry oligo, target 100 μM stock concentration:

  • n = 100 nmol = 100 × 10⁻⁹ mol = 10⁻⁷ mol
  • C = 100 μM = 100 × 10⁻⁶ mol/L = 10⁻⁴ mol/L
  • V = 10⁻⁷ / 10⁻⁴ = 10⁻³ L = 1 mL = 1000 μL

This is THE recipe printed on every IDT order — add 1 mL of buffer to 100 nmol of oligo to get a 100 μM stock. Memorize it; you'll use it a thousand times in your career.

Quick Mental-Math Shortcuts

  • nmol / μM = μL. So 25 nmol / 100 μM = 250 μL. Easy to memorize because the prefix ratio (nano / micro = 1/1000 = milli, then × 10⁶ for μL) reduces to 1.
  • nmol / mM = nL. 100 nmol / 1 mM = 100 nL — way too small to pipette; bump down to μM range.
  • μmol / μM = L. 1 μmol / 100 μM = 10 mL. For larger oligo orders.
  • For 100 μM target: volume in μL = amount in nmol × 10. So 25 nmol → 250 μL, 100 nmol → 1000 μL = 1 mL, 250 nmol → 2500 μL.
  • For 1 mM target: volume in μL = amount in nmol. So 100 nmol → 100 μL, 250 nmol → 250 μL.

Choosing the Right Target Concentration

The target concentration determines both the practical pipetting volume AND the working dilution factor. Common choices:

  • 100 μM (default): Standard primer stock. Dilute 100× into PCR for ~1 μM final concentration. Convenient pipetting volumes for typical synthesis scales.
  • 1 mM: Concentrated master stock. Smaller storage volumes; useful when freezer space is limited. Dilute 1000× for PCR.
  • 10 μM: Pre-diluted working stock. Saves a dilution step at the bench but uses 10× more freezer space.
  • 200 μM: Very-high-conc stocks for low-volume reactions or limited starting material.

Choosing the Right Buffer

  • TE buffer (Tris-EDTA): 10 mM Tris-HCl pH 8.0 + 1 mM EDTA. The standard for long-term DNA storage. EDTA chelates divalent cations (Mg²⁺) that activate trace nucleases — protects against degradation. Slightly inhibits PCR if not diluted appropriately.
  • Nuclease-free water: For short-term work (days to weeks) or when downstream protocols don't tolerate EDTA. Less protective long-term but doesn't affect any reactions.
  • 10 mM Tris-HCl pH 8.0 (no EDTA): Compromise — buffered (pH protective) but no EDTA interference.
  • RNase-free water: Required for RNA oligos. Never reuse a stock — RNases are everywhere.
  • DEPC-treated water: RNase-free option; once standard but DEPC residue can interfere with some assays.

When V = n / C Doesn't Apply

  • dsDNA / plasmid concentration in ng/μL. The IDT report for dsDNA gBlocks reports mass, not moles. Convert first: M (mol/L) = (ng/μL) × 1000 / (660 × bp), where 660 is the average dsDNA molecular weight per base pair (g/mol).
  • Protein in mg/mL. Use M = (mg/mL) × 1000 / MW_protein, where MW is in Daltons (= g/mol).
  • Mixtures. The formula assumes a single-component solute. For mixtures (e.g., random hexamers, dNTP mix), each component has its own concentration.
  • Volume change on dissolution. For very concentrated stocks (> 100 mg/mL), the dissolved solute occupies non-negligible volume — V_final > V_solvent_added. Negligible for typical oligo work.
Real-World Example

Resuspension Calculator – Worked Examples

Example 1 — Standard PCR Primer (the Classic Recipe). A 100 nmol scale primer order arrives from IDT. Make a 100 μM stock.
  • n = 100 nmol = 10⁻⁷ mol; C = 100 μM = 10⁻⁴ M.
  • V = n/C = 10⁻⁷ / 10⁻⁴ = 10⁻³ L = 1.000 mL = 1000 μL.
  • Recipe: Add 1 mL of TE buffer (or nuclease-free water) to the dry oligo pellet. Vortex briefly, let stand 5-10 min, centrifuge to collect.
  • Working concentration: dilute 1 μL stock + 99 μL buffer (or directly into a 100 μL PCR reaction) for 1 μM final.
  • This is THE most common resuspension calculation in molecular biology — you'll do it hundreds of times.

Example 2 — Small Primer Order (25 nmol). Make a 100 μM stock from a 25 nmol scale primer.

  • n = 25 nmol; C = 100 μM.
  • V = 25 nmol / 100 μM = 250 μL. Mental-math shortcut: nmol × 10 = μL at 100 μM.
  • This is at the boundary of the "tight" pipetting band — 250 μL is comfortable with a P200 or P1000.

Example 3 — Concentrated Master Stock (1 mM). 100 nmol oligo at 1 mM target.

  • n = 100 nmol = 10⁻⁷ mol; C = 1 mM = 10⁻³ M.
  • V = 10⁻⁷ / 10⁻³ = 10⁻⁴ L = 100 μL.
  • 10× more concentrated than the standard 100 μM stock; 10× less freezer space. Useful when storing many oligos in a single tube rack — saves space at the cost of pipetting precision (you'll use 10× less per reaction).

Example 4 — Large Oligo Order (1 μmol). 1 μmol of an oligo at 100 μM target.

  • n = 1 μmol = 10⁻⁶ mol; C = 100 μM = 10⁻⁴ M.
  • V = 10⁻⁶ / 10⁻⁴ = 10⁻² L = 10 mL.
  • 10 mL is a large stock — usually divided into ~10 × 1-mL aliquots for storage. Avoid repeated freeze-thaw of large stocks (degrades over time); aliquots minimize freeze-thaw cycles.

Example 5 — CRISPR Guide RNA (sgRNA). 1 mg of synthesized sgRNA (~100 nt, MW ≈ 32,500 g/mol) at 100 μM target. First convert mass to moles.

  • Moles: n = 1 mg / 32,500 g/mol = 1×10⁻³ / 32500 = 3.08×10⁻⁸ mol = 30.8 nmol.
  • V = 30.8 nmol / 100 μM = 308 μL. Round to 300 μL for convenience.
  • Use RNase-free water (NOT TE — EDTA can interfere with some downstream Cas9 assays). Aliquot immediately into 50 μL portions and freeze at −80 °C.

Example 6 — siRNA for Knockdown (Bad Calculation Catch). 100 μg siRNA (~13,500 g/mol) at 1 μM target. Sounds simple but check the volume:

  • Moles: n = 100×10⁻⁶ g / 13,500 g/mol = 7.4×10⁻⁹ mol = 7.4 nmol.
  • V = 7.4 nmol / 1 μM = 7.4 nmol / 1×10⁻⁶ M = 7.4×10⁻³ L = 7.4 mL.
  • That's a lot of volume for a small amount of expensive siRNA! Make a more concentrated stock instead: at 100 μM, V = 74 μL — much more practical and saves freezer space. Dilute serially down to 1 μM working concentration when needed.

Who Should Use the Resuspension Calculator?

1
Molecular Biology Students: Learn the V = n/C calculation that every wet-lab biologist uses; understand the IDT/Sigma standard recipes.
2
PCR Primer Designers: Fresh primer stocks every day — quickly compute the buffer volume for any synthesis scale and target stock concentration.
3
CRISPR-Cas9 Researchers: Resuspend synthesized guide RNAs (sgRNA, crRNA, tracrRNA) at appropriate concentrations for transfection and in vitro digestion.
4
siRNA / shRNA Users: Prepare gene-knockdown reagents at standard 100 μM stock concentrations; aliquot for single-use to avoid freeze-thaw degradation.
5
Synthetic Biology Engineers: Resuspend gBlocks, ssDNA fragments, and assembly oligos at concentrations compatible with Gibson assembly or Golden Gate protocols.
6
Protein Chemists: Lyophilized peptides and small proteins — apply the same V = n/C principle with appropriate molecular weights.

Technical Reference

Standard Oligo Synthesis Scales (Commercial). Commercial DNA synthesis vendors (IDT, Sigma-Aldrich, Thermo Fisher, Eurofins) produce oligos at standardized scales:

  • 25 nmol scale: ~$10-20 per primer; 4-5 nmol typical actual yield. Resuspend in 250 μL for 100 μM stock.
  • 100 nmol scale (most common): ~$15-30; 30-50 nmol typical yield (some loss during deprotection). Resuspend in 1 mL for 100 μM.
  • 250 nmol scale: ~$50-80; 100-150 nmol yield. Resuspend in 2.5 mL for 100 μM (typically aliquoted into 5 × 500 μL).
  • 1 μmol scale: ~$200-400; 400-600 nmol yield. Industrial / large-prep scale. 10 mL for 100 μM.
  • 10 μmol+ scale: Custom large-scale orders for diagnostics/therapeutics; 100+ mL stocks.

Standard Buffers for Resuspension:

  • TE buffer (10 mM Tris, 1 mM EDTA, pH 8.0): Universal long-term DNA storage standard. Recipe: 10 mL of 1 M Tris-HCl pH 8.0 + 2 mL of 0.5 M EDTA pH 8.0 + water to 1 L. Sterilize by autoclaving or 0.22 μm filter.
  • TE-low (10 mM Tris, 0.1 mM EDTA, pH 8.0): Less EDTA — better for downstream PCR/enzymatic work that's EDTA-sensitive. The default for many siRNA suppliers.
  • Nuclease-free water: Commercial product (Ambion, Invitrogen, etc.) certified DNase- and RNase-free. ~$50/500 mL. For short-term storage.
  • RNase-free water for RNA: DEPC-treated and autoclaved, OR commercial certified RNase-free. RNases are notoriously persistent — single-use aliquots only.
  • 1× PBS (phosphate-buffered saline): For some peptide / protein resuspension; isotonic with cells. NOT for DNA storage (no EDTA protection).

Common Reference Recipes (V = n / C):

  • 100 nmol oligo / 100 μM: 1.000 mL (the universal IDT default)
  • 250 nmol oligo / 100 μM: 2.500 mL
  • 1 μmol oligo / 100 μM: 10.000 mL
  • 100 nmol / 1 mM: 100 μL (concentrated stock)
  • 100 nmol / 10 μM: 10 mL (pre-diluted working)
  • 1 nmol primer / 10 μM: 100 μL
  • 10 nmol primer / 100 μM: 100 μL
  • 100 μg dsDNA (3 kb) / 100 ng/μL: 1 mL (mass concentration, not molar)
  • 100 μg siRNA (20 nt) / 100 μM: ~75 μL
  • 1 mg sgRNA (100 nt) / 100 μM: ~290 μL

dsDNA Mass-to-Molarity Conversion. dsDNA concentration is often reported in ng/μL rather than molarity. Convert via the average dsDNA molecular weight: MW(dsDNA) ≈ 660 × N g/mol, where N is the number of base pairs. So molarity = (ng/μL) × 1000 / (660 × bp) in nM, or = (ng/μL) / (0.66 × bp) in μM. Example: 100 ng/μL of a 3,000 bp plasmid → 100 / (0.66 × 3000) = 0.0505 μM = 50.5 nM. For ssDNA, use 330 × N (single-strand factor).

Storage and Stability. Resuspended oligos are stable for years if stored properly: −20 °C standard freezer for working stocks (years for DNA, months for RNA); −80 °C for long-term archive (decades for DNA, years for RNA); 4 °C only for active use (weeks for DNA, days for RNA). Avoid repeated freeze-thaw cycles — RNA degrades 5-15% per cycle, DNA 1-5% per cycle. Aliquot into single-use volumes (typically 50-100 μL) to minimize freeze-thaw.

Pipetting Precision Limits:

  • P2 (0.1-2 μL): ±5-10% accuracy at 1 μL; not recommended below 0.5 μL
  • P10 (1-10 μL): ±2-5% accuracy
  • P20 / P200 / P1000 (mid-range): ±1-2% accuracy in the middle of their range
  • Serological pipettes (1-50 mL): ±0.5-1% accuracy

For volumes < 1 μL, accuracy degrades sharply — better to make a higher-concentration stock and dilute serially than to attempt sub-microliter pipetting.

Conversion Quick Reference for the V = n/C formula. SI prefix relationships: nano (10⁻⁹) / micro (10⁻⁶) = 10⁻³ = milli; pico / nano = milli; pico / micro = micro; micro / micro = 1. So nmol/μM = (10⁻⁹ mol) / (10⁻⁶ mol/L) = 10⁻³ L = mL. Wait, that's mL not μL — let me recheck. (100×10⁻⁹ mol) / (100×10⁻⁶ mol/L) = 10⁻³ L = 1 mL = 1000 μL. So actually (amount in nmol) / (conc in μM) gives volume in mL × 1, since the prefixes cancel as 10⁻³. The "nmol × 10 = μL at 100 μM" mental shortcut works for the specific case of 100 μM.

Key Takeaways

Resuspension is the simplest molecular-biology calculation: V = n / C. Volume of buffer to add equals moles of solute divided by target molar concentration. The universal default recipe — 100 nmol oligo + 1 mL = 100 μM stock — is what every commercial DNA synthesis vendor recommends; memorize it once and you'll never need to recalculate it. For other concentrations, useful mental-math shortcuts: nmol / μM = μL; nmol / mM = nL; μmol / μM = mL × 10. Choose the right buffer (TE for long-term DNA storage; nuclease-free water for short-term; RNase-free water for RNA), vortex briefly to dissolve, aliquot to minimize freeze-thaw cycles, and store at −20 °C (or −80 °C for RNA / long-term). Use the ToolsACE Resuspension Calculator with 7 amount units, 9 concentration units, auto-pick volume display, 5-band pipetting class check, and 9 reference scenarios from the universal 100 nmol/100 μM through CRISPR gRNA preps. Bookmark it for daily molecular biology — you'll use it more often than any other tool in your bench arsenal.

Frequently Asked Questions

What is the Resuspension Calculator?
It computes the volume of buffer to add when resuspending a lyophilized oligonucleotide (or other solute) to a target stock concentration, using the universal stoichiometry formula V = n / C. Inputs: oligo amount n in 7 unit options (mol, mmol, μmol, nmol, pmol, fmol, amol — covering all commercial synthesis scales) and desired concentration C in 9 unit options (M, mM, μM, nM, pM, fM, aM, zM, yM). Output: volume in any of 5 units (auto-picks the most readable: μL for typical preps, mL for larger, L for industrial), 5-band pipetting class check (too-small / tight / good / large / huge), full step-by-step breakdown, and 9 reference scenarios.

Designed for molecular biology students, PCR primer designers, CRISPR researchers, siRNA users, synthetic biology engineers, and protein chemists. Runs entirely in your browser — no data stored.

Pro Tip: Use our Molarity Calculator to convert ng/μL (mass) to molarity for dsDNA preps.

What's the formula for resuspension volume?
V = n / C, where V is the volume of buffer to add, n is the moles of solute being dissolved, and C is the target molar concentration. Result is in liters when n is in mol and C is in mol/L. Direct rearrangement of the molarity definition (M = mol / L → L = mol / M).
What's the standard recipe for oligo resuspension?
100 nmol oligo + 1 mL buffer = 100 μM stock. This is the universal default at IDT, Sigma-Aldrich, Thermo Fisher, and every commercial DNA synthesis vendor. Verify: V = 100 nmol / 100 μM = 100×10⁻⁹ mol / 100×10⁻⁶ M = 10⁻³ L = 1.000 mL. ✓ The 100 μM stock is conveniently a 100× concentrate for typical 1 μM working PCR primer concentrations.
What buffer should I use?
TE buffer (10 mM Tris-HCl pH 8.0, 1 mM EDTA) for long-term DNA storage — the EDTA chelates divalent cations that activate trace nucleases, protecting oligos against degradation. Nuclease-free water for short-term work or when downstream protocols don't tolerate EDTA. TE-low (0.1 mM EDTA) as a compromise. RNase-free water required for RNA oligos — never reuse the same stock to avoid RNase contamination. Never use unsterile water — even trace nucleases will degrade oligos overnight.
How long are resuspended oligos stable?
DNA oligos: Years at −20 °C in TE buffer; decades at −80 °C. Stable at 4 °C for weeks. RNA oligos: Months at −20 °C; years at −80 °C in RNase-free conditions. Days at 4 °C. Always aliquot into single-use volumes (50-100 μL typical) to minimize freeze-thaw cycles — RNA degrades 5-15% per cycle, DNA 1-5% per cycle. After ~5 freeze-thaws, accuracy of subsequent experiments suffers noticeably.
Why is 100 μM the standard target?
Three reasons: (1) Convenient pipetting volumes — for the standard 100 nmol synthesis scale, 100 μM gives exactly 1 mL, easy to pipette; (2) 10× / 100× dilution math — most PCR primers work at 0.1-1 μM final, which is a 100× to 1000× dilution from the stock; (3) Universal vendor standard — every commercial synthesis vendor prints "resuspend in X μL for 100 μM stock" on the packaging, so all collaborators are on the same page. Other common targets (1 mM for concentrated, 10 μM for pre-diluted) all derive from this reference.
How do I convert ng/μL to molarity for dsDNA?
Use the average dsDNA molecular weight: MW(dsDNA) ≈ 660 × bp g/mol per base pair. So molarity (in nM) = (ng/μL) × 1000 / (660 × bp), or molarity (in μM) = (ng/μL) / (0.66 × bp). Example: 100 ng/μL of a 3,000 bp plasmid → 100 / (0.66 × 3000) = 0.0505 μM = 50.5 nM. For ssDNA, use 330 × bp instead of 660. Once you have molarity, you can use the V = n/C formula directly.
What if my calculated volume is too small to pipette?
If V < 1 μL, you've hit the practical pipetting limit. Three options: (1) Reduce target concentration — if you computed 0.5 μL for 1 mM stock, try 100 μM instead (10× dilution → 5 μL, easy to pipette). (2) Make a larger volume of stock if your synthesis scale was very small. (3) Use a higher-concentration stock and dilute serially — make 1 mM, then dilute to working concentration in PCR. Sub-microliter pipetting (P0.5 or P2 at the bottom of range) has ±5-10% accuracy, which propagates into significant concentration variability.
What if my volume is too large to be practical?
If V > 100 mL, your target concentration is probably too dilute. Make a more concentrated stock (e.g., 100 μM instead of 1 μM — 100× less volume) and dilute serially when needed. Very-low-concentration stocks waste freezer space and often expire (DNA at 1 nM is hard to detect spectroscopically — you can't easily verify the concentration is what you think it is).
Should I use TE or water?
For long-term storage (months to years) or oligos you'll use repeatedly: TE buffer. The EDTA chelates Mg²⁺/Ca²⁺ that activate trace nucleases. The 10 mM Tris also buffers against pH drift. For short-term storage (days to weeks) or when downstream applications are EDTA-sensitive (some real-time PCR setups, Cas9 in vitro digestion): nuclease-free water. For RNA: ALWAYS RNase-free water (never reuse aliquots; RNases are everywhere). For peptides/proteins: depends on the protein — TE for nucleic-acid-binding proteins, PBS for cell-secreted proteins, custom buffer per protocol.
How precise does my pipetting need to be?
For most molecular biology work, ±5% concentration accuracy is fine — corresponds to ±5% pipetting precision (achievable with any standard P10/P20/P200/P1000 micropipette in their middle range). For quantitative PCR with absolute concentration standards, ±2% is needed — use freshly calibrated pipettes and reverse-pipetting technique. For dilution series spanning many orders of magnitude (qPCR standards, ELISA standards), pipette in the middle of each pipette's range and verify with absorbance at A260 or fluorescent dye binding. Sub-microliter pipetting has inherent ±5-10% error — make higher-concentration stocks and dilute, rather than direct sub-μL transfers.

Author Spotlight

The ToolsACE Team - ToolsACE.io Team

The ToolsACE Team

Our chemistry tools team implements the universal resuspension formula every molecular biologist uses every week: <strong>V = n / C</strong>, where V is the volume of buffer to add, n is the moles of lyophilized material in the tube (from the synthesis report), and C is the target stock concentration. The standard recipe — <strong>100 nmol oligo + 1 mL = 100 μM stock</strong> — is the default at IDT, Sigma, Thermo Fisher, and every commercial DNA synthesis vendor; it gives a 100× concentrate for typical 1 μM working PCR primers. The calculator handles 7 amount units (mol → amol covering all synthesis scales) and 9 concentration units (M → yM covering ultra-dilute trace assays) with automatic SI normalization. Output: buffer volume in any of 5 units (auto-picks the most readable) plus a 5-band pipetting class check (too-small, tight, good, large, huge) that flags volumes below ~1 μL (impractical to pipette accurately) or above ~100 mL (probably means wrong inputs — too-dilute target). Reference table includes 9 standard scenarios from the universal 100 nmol/100 μM through CRISPR gRNA, siRNA knockdown, and large dsDNA preps.

Molecular BiologyOligo Resuspension ProtocolsSoftware Engineering Team

Disclaimer

The calculator gives the volume to make a stock at the target molar concentration. For typical lab use: TE buffer (10 mM Tris-HCl pH 8.0, 1 mM EDTA) for long-term DNA storage; nuclease-free water for short-term work. RNA oligos require RNase-free water and single-use aliquots. For dsDNA / plasmids: ng/μL ≠ molarity — convert via M = (ng/μL) / (0.66 × bp) before using this calculator. Pipetting precision: P10/P20 micropipettes typical ±2-5% accuracy at 1-2 μL; for volumes < 1 μL, use a higher-concentration stock and dilute serially. The formula assumes the dissolved solute occupies negligible volume (true for dilute oligos; not for very concentrated peptide / protein preps).