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🧬

DNA Copy Number from Mass

Copies = mass × 6.022×10²³ / (length × 660). Converts ng/µL to molecular count for qPCR standards, viral load, and NGS.

Concept Fundamentals
Copies = C×N_A/(l×W_bp)
Formula
660 Da/bp
dsDNA
N = i × 2ⁿ
PCR
10¹–10¹⁰ copies/µL
qPCR
Calculate DNA Copy NumberAvogadro-based mass-to-copy conversion

Why This Biology Metric Matters

Why: Copy number is essential for qPCR standard curves, viral load quantification, and NGS library normalization.

How: Use concentration (ng/µL), template length (bp), and base weight (dsDNA 660, ssDNA 330, ssRNA 340 Da). PCR: N = initial × 2^cycles.

  • ●50 ng/µL 5 kb plasmid ≈ 10¹⁰ copies/µL — ideal for qPCR standards.
  • ●Shorter fragments yield more copies per ng; 250 bp has ~20× more than 5 kb.
  • ●Real PCR efficiency ~90–95%; theoretical 2^n assumes 100%.
Sources:NEBMolecular Cloning (Sambrook)

Calculate DNA copy number from concentration using Avogadro's constant. Supports dsDNA, ssDNA, ssRNA, PCR amplification, and qPCR standard preparation.

📋 Compact Examples

Plasmid DNA Standard

Typical qPCR standard preparation (5000 bp plasmid, 50 ng/µL)

PCR Product Quantification

Amplified PCR product (250 bp amplicon, 20 ng/µL)

Viral Genome Copies

Viral RNA quantification (10 kb genome, 100 ng/µL)

Genomic DNA Copy Number

Human genomic DNA (3 Gb genome, 50 ng/µL)

Input Parameters

Enter Parameters

ng/µL

For educational use only. Always confirm dosages and care with a licensed veterinarian.

🧬 Biology Facts

📐

Copies/µL = (C × N_A) / (length × base weight). N_A = 6.022×10²³.

— Formula

🧬

dsDNA: 660 Da/bp; ssDNA: 330 Da/nt; ssRNA: 340 Da/nt.

— Base weights

🔬

PCR doubles DNA each cycle; 30 cycles from 1 copy ≈ 1 billion.

— PCR

📊

qPCR standards typically span 10¹–10¹⁰ copies/µL in log10 dilutions.

— qPCR

📋 Key Takeaways

  • • Copies/µL = (C_DNA × N_A) / (l × 10⁹ × W_bp) — converts mass to molecular count.
  • • Avogadro's constant (6.022×10²³) links grams to molecule count.
  • • dsDNA: 660 Da/bp; ssDNA: 330 Da/nt; ssRNA: 340 Da/nt.
  • • PCR: N = i × 2^n. Real efficiency ~90–95%. Use for qPCR standards, viral load, NGS.

💡 Did You Know?

🧬A 50 ng/µL 5 kb plasmid yields ~10¹⁰ copies/µL — ideal for qPCR standards.Source: Molecular biology
📊Avogadro's constant converts 1 mole of any substance to 6.022×10²³ molecules.Source: Chemistry
🔬PCR doubles DNA each cycle — 30 cycles from 1 copy = 1 billion copies.Source: PCR theory
🦠Viral load uses ssRNA weight (340 Da/nt) for RNA virus quantification.Source: Virology
📐Shorter fragments = more copies per ng. 250 bp amplicon has 20× more copies than 5 kb.Source: Fragment size
🧪qPCR standards typically span 10¹–10¹⁰ copies/µL. Log10 dilutions.Source: qPCR

📖 How DNA Copy Number Calculation Works

Convert DNA concentration (ng/µL) to molecular count using Avogadro's constant and template length.

Formula

Copies/µL = (C_DNA × N_A) / (l × 10⁹ × W_bp)

C_DNA = ng/µL; N_A = 6.022×10²³; l = bp; W_bp = 660 (dsDNA), 330 (ssDNA), 340 (ssRNA)

🎯 Expert Tips

💡 Use Accurate Concentration

Qubit or Nanodrop. Verify recent. Degraded DNA = shorter lengths.

💡 Log10 Dilutions

qPCR standards: 10⁶, 10⁵, 10⁴... Gel electrophoresis confirms size.

💡 PCR Efficiency

Theory assumes 100%. Real PCR ~90–95%. Use qPCR during exponential phase.

💡 GC Content

High GC may affect MW slightly. Average weights work for most applications.

⚖️ Base Weight Comparison

TypeWeightUse Case
dsDNA660 Da/bpPlasmids, genomic DNA, PCR products
ssDNA330 Da/ntSingle-stranded DNA, oligonucleotides
ssRNA340 Da/ntViral RNA, mRNA, RNA quantification

❓ Frequently Asked Questions

How do I convert ng/µL to copies/µL?

Use formula: Copies/µL = (C × N_A) / (MW). MW = length × base weight. This calculator does it for you.

Can I use this for RNA?

Yes. Select ssRNA (340 Da/nt) for viral RNA, mRNA, or RNA quantification.

Why does PCR use 2^n?

Each cycle doubles DNA. 1 copy → 2 → 4 → 8... 30 cycles = 2³⁰ ≈ 1 billion.

What if my fragment is degraded?

Use actual measured length. Degraded DNA has shorter average length—copy number will be higher per ng.

How accurate is qPCR copy number?

Standards ±10–20% typical. Use log10 dilutions for calibration curves.

Can I use for CRISPR guide RNA?

Yes. Use ssRNA for RNA guides. Calculate copies for optimal editing efficiency.

📊 DNA Copy Number by the Numbers

6.022×10²³
Avogadro constant
660
Da/bp dsDNA
2^n
PCR per cycle
10¹–10¹⁰
qPCR copies/µL

⚠️ Disclaimer: Educational only. Calculations use standard formulas. Verify concentration with Nanodrop/Qubit. Base weights are averages; GC content may vary. For clinical or regulatory use, consult lab protocols.

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