Enter Calculation Details
Paste a DNA sequence, select the molecular form, and optionally calculate preparation quantities.
Example Data
This example shows how an entered sequence becomes a molecular-weight estimate.
| Input | Example value | Why it matters |
|---|---|---|
| DNA sequence | ATGCGTAC |
Eight bases are evaluated in the submitted order. |
| DNA form | Single-stranded | Only the entered oligonucleotide contributes to the total. |
| Available amount | 25 pmol | The tool converts this molar amount into mass. |
| Target solution | 10 µM in 100 µL | The tool calculates the moles and mass required. |
Formula Used
Single-strand molecular weight = Σ(base residue masses) + 18.01528 Da + custom adjustment.
Double-strand molecular weight = entered strand mass + complementary strand mass + custom adjustment.
Sample mass = molecular weight (g/mol) × amount (mol).
Target moles = concentration (mol/L) × volume (L). Target mass = target moles × molecular weight.
Average DNA residue masses used: A 313.21, T 304.20, C 289.18, and G 329.21 Da. Ambiguity symbols use the mean of their possible bases.
How to Use This Calculator
- Paste the DNA sequence into the sequence box.
- Select single-stranded or double-stranded DNA.
- Choose how uracil should be handled.
- Add a documented custom mass adjustment when needed.
- Optionally enter available amount, target concentration, and final volume.
- Press Calculate DNA Mass and review the output above the form.
DNA Sequence Mass Planning Guide
Start With the Sequence
DNA mass begins with the sequence itself. Each DNA base has a different average molecular mass. Adenine, thymine, cytosine, and guanine contribute predictable residue values. The calculator cleans the submitted sequence before calculating. Spaces, line breaks, and FASTA headers are ignored. Standard ambiguity codes are also supported. Their values use the average of possible bases. This makes preliminary planning easier when some positions remain uncertain.
Select the Correct Molecular Form
A single strand is measured as one oligonucleotide. Its molecular weight equals the sum of nucleotide residue masses. The calculator then includes terminal chemistry for free hydroxyl ends. A double strand includes the entered sequence and its complement. The result represents the entire duplex. The entered sequence length becomes the base-pair count. Total nucleotide count doubles for duplex DNA. Select the correct form before using any mass result.
Read Composition Carefully
Base composition helps explain the calculated number. Guanine is heavier than cytosine, while adenine is heavier than thymine. Therefore, sequences with equal lengths can have different masses. GC percentage is also displayed. This value can guide melting-temperature discussions and sequence comparisons. It does not replace a complete thermodynamic analysis. Ambiguous letters create expected base counts. These counts may contain decimal values.
Convert Moles Into Mass
The calculator can turn a molar amount into a sample mass. Enter a value in femtomoles, picomoles, nanomoles, micromoles, millimoles, or moles. The tool multiplies the molecular weight by the amount in moles. Results are shown using practical mass units. This is useful when ordering material or preparing stock solutions. Always confirm whether your supplier reports dry mass, salt form, or modified mass.
Prepare a Target Solution
You can also enter a target concentration and final volume. The calculator first finds required moles using concentration multiplied by volume. It then converts those moles into mass. This helps prepare small reactions and larger stock batches. When a supplied amount and target concentration are both entered, the calculator estimates the final volume. Use consistent laboratory units. Check pipetting limits before making very dilute solutions.
Use Adjustments With Evidence
Custom mass adjustment accepts positive or negative dalton values. Use it for labels, terminal changes, or known chemical differences. Apply only values supported by your reagent documentation. The built-in base masses are average planning values. Exact mass may vary with isotope selection, salt state, modifications, hydration, and vendor conventions. Treat the result as a strong calculation aid. Review critical production work with the relevant protocol.
Verify the Input Before Preparation
Sequence quality matters. Remove primers, adapters, and non-DNA characters when they are not part of the analyte. Confirm orientation before ordering complement-sensitive products. A reverse complement is not automatically substituted. The calculator uses the entered strand directly. For plasmids or long genomic fragments, large-number rounding may reduce displayed detail. Exporting results preserves the values for records.
Keep a Traceable Record
Use a verified sequence. Copying errors can change both composition and molecular weight. Check unusual letters against IUPAC notation. Replace RNA uracil only when that conversion matches your intended molecule. The sequence preview confirms the cleaned input.
Frequently Asked Questions
1. What sequence letters can I enter?
You can enter A, T, C, and G. The calculator also accepts standard IUPAC ambiguity codes, including R, Y, S, W, K, M, B, D, H, V, and N. Ambiguity letters use average values from their possible bases.
2. Does the calculator accept FASTA input?
Yes. Lines beginning with the greater-than symbol are ignored as FASTA headers. Spaces, line breaks, and numeric position labels are also removed before the DNA sequence is checked.
3. Why can equal-length sequences have different masses?
The four DNA bases have different residue masses. A guanine-rich sequence usually weighs differently from a thymine-rich sequence of the same length. The base composition therefore changes molecular weight.
4. What is included for double-stranded DNA?
The calculator adds the entered DNA strand and its complementary strand. The sequence length is reported in base pairs, while the total nucleotide count includes both strands.
5. Can I use RNA sequences?
You can choose to treat U as T for a thymine-equivalent planning estimate. That option is not an exact RNA mass calculation. Select reject U when you need strict DNA-only validation.
6. What does the custom adjustment do?
It adds or subtracts a user-supplied dalton value from the final molecular weight. Use it for known modifications, labels, or terminal chemistry. Verify the correction with reagent documentation.
7. How is the required mass for a solution calculated?
The calculator multiplies target concentration by final volume to find moles. It then multiplies those moles by molecular weight. Enter both concentration and volume to receive this result.
8. Is the extinction coefficient exact?
No. It is a rough base-count estimate using single-base coefficients. Highly accurate absorbance work often uses nearest-neighbor methods and vendor-specific settings.
9. Why are some base counts decimal values?
Ambiguity codes represent multiple possible bases. The calculator divides one position across those possibilities. For example, N contributes one-quarter each to A, T, C, and G expected counts.
10. Can I download my calculation?
Yes. After calculating, use Download CSV for a spreadsheet-friendly file. Use Print / Save PDF to create a printable record from your browser.
11. Should I use this result for critical manufacturing?
Use the calculator as a planning aid. Confirm exact mass, modifications, salts, and supplier conventions before regulated, clinical, or production work. Follow your approved laboratory procedure.