Input
Average methods are widely used for plasmids.
If sequence provided, this updates automatically.
Detected length: 0 nt
GC%: 0.0%
Composition A/C/G/T: 0/0/0/0
Adds ~14.0157 Da per methylation.
Optional fixed mass to add.
Primers/tags to add to length.
Calculates molecule copies for the mass.
Overrides average constant for advanced cases.
Avogadro's number = 6.02214076×10^23
Molecular weight
— Da
= — g/mol
Stoichiometric helpers
ng per pmol: —
pmol per μg: —
Copies from sample
Molecules in sample: —
Uses provided sample mass.
Results Log
| # | Label | Mode | Strand | Length (bp/nt) | Methyl | Extra Da | MW (Da) | ng/pmol | pmol/μg | Copies (sample) |
|---|
Example plasmids
| Plasmid | Size (bp) | MW (660×bp, Da) | |
|---|---|---|---|
| pUC19 | 2686 | ||
| pBR322 | 4361 | ||
| pET-28a(+) | 5369 | ||
| pGEM-T Easy | 3015 | ||
| pEGFP-N1 | 4733 |
MW here uses 660 Da per bp approximation.
Formulas Used
- MWavg ≈ bp × k, with k = 650–660 Da per base pair for dsDNA.
- Single-stranded approximation uses ~330 Da per nucleotide.
- Sequence estimate (from one strand, dsDNA):
MW ≈ 2×(313.21·A + 289.18·C + 329.21·G + 304.20·T) − 2×(n−1)×18.015
where n = A+C+G+T and 18.015 accounts for water loss per phosphodiester bond. - Methylation adds ~14.0157 Da per methylated base. Additional modifications add their entered mass.
- ng per pmol = MW / 1000; pmol per μg = 106 / MW.
- Copies in sample (from ng): copies = (ng × 1e−9 / MW) × NA, with NA=6.02214076×1023.
These approximations are standard for plasmid sizing and most prep calculations.
Conversion Quick Reference (660 Da/bp)
Computed for circular dsDNA using 660 Da per base pair. Copies per ng use Avogadro's number.
| Size (bp) | MW (Da) | ng per pmol | pmol per μg | Copies per ng |
|---|
Effect of Extra Bases (Added Primers/Tags)
Assumes dsDNA and 660 Da per base pair. Percent change is relative to a 3000 bp plasmid.
| Extra bases | Added mass (Da) | Added ng per pmol | Δ copies per ng (vs 3 kb) | % mass change (vs 3 kb) |
|---|
How to Use
- Select a calculation mode and enter length in base pairs.
- Alternatively, paste one-strand sequence; length and GC% populate automatically.
- Choose strandness. Typical plasmids are double-stranded.
- Optionally add methylations, extra mass in Daltons, or extra bases.
- Provide a sample mass in ng to compute molecule copies.
- Click Calculate, then Add to results to log a row.
- Use Download CSV or Download PDF to export the table.
Tip: Use the example plasmids to prefill common sizes and verify outputs.