Primary formula
Wallace rule: Tm ≈ 2(A + T) + 4(G + C) °C. Basic GC formula: Tm ≈ 64.9 + 41(G + C − 16.4)/length.
Biology calculator
DNA Melting Temperature Calculator
Estimate an oligonucleotide melting temperature from a DNA sequence or A, T, G and C counts.
Last reviewed: August 5, 2026Biology calculation engine v3.0.0
DNA Melting Temperature Calculator
Estimate an oligonucleotide melting temperature from a DNA sequence or A, T, G and C counts.
Apply the Wallace rule to an ATGC sequence.
Formula and assumptions
Input assumptions
Only A, T, G and C are accepted. The selected empirical formula is appropriate for the intended screening use. The sequence is unmodified.
Precision note
Biology models use Decimal.js for deterministic arithmetic where useful, with documented local constants for DNA base contributions.
How NexaCalc calculates biology results
Validate
Required numeric, count, frequency and DNA sequence inputs are checked before calculation.
Model
The selected Biology formula or model is applied in a pure TypeScript utility.
Explain
The result card shows formula substitutions, assumptions, warnings and related values.
Visualize
A scenario-specific Biology visual appears only after a valid calculation.
What the DNA Melting Temperature Calculator does
Use this tool for a quick DNA melting-temperature estimate from base composition.
DNA Melting Temperature Calculator calculates locally and separates formula, variables, assumptions, examples, warnings and references so the result can be checked without external biology APIs.
Formula or model and variables
Wallace rule: Tm ≈ 2(A + T) + 4(G + C) °C. Basic GC formula: Tm ≈ 64.9 + 41(G + C − 16.4)/length.
- A, T, G and C are base counts.
- Length is the total ATGC count.
- The output can be shown in °C, °F or K.
Step-by-step worked example
Use the default values as the worked example for DNA Melting Temperature Calculator. After Calculate, the result card shows the substituted model and a breakdown using the same engine values.
The examples are intentionally simple so the formula direction and biological assumptions are visible.
- ATGC contains two AT and two GC bases, giving 12°C with the Wallace rule.
- AATTGGCC gives 24°C with the Wallace rule.
- The basic GC formula is intended for longer sequences and remains an approximation.
Additional examples
These additional examples use the same deterministic model path.
- ATGC contains two AT and two GC bases, giving 12°C with the Wallace rule.
- AATTGGCC gives 24°C with the Wallace rule.
- The basic GC formula is intended for longer sequences and remains an approximation.
How to read the dynamic biology visual
The visual for this page is a DNA duplex with AT and GC melting contributions. It appears only after Calculate, so there is no fake default result.
Visual proportions are normalized for readability and should be read as explanatory diagrams, not measured laboratory diagrams.
Common mistakes
Most errors come from model mismatch, invalid input meaning or over-interpreting a simplified estimate.
- Using ambiguous bases without an explicit rule.
- Treating a composition-only estimate as a complete primer-design result.
- Ignoring salt, magnesium, mismatches or secondary structure.
Assumptions and limitations
Biology calculators are simplified models. They help with education and planning, but real organisms, lab systems and datasets can behave differently.
- Only A, T, G and C are accepted.
- The selected empirical formula is appropriate for the intended screening use.
- The sequence is unmodified.
- Measured Tm depends on assay chemistry and sequence context.
- This tool does not model salt, magnesium, mismatches, dimers or hairpins.
Practical and lab-use note
This calculator is for general educational use only. It does not replace laboratory protocols, institutional guidance, safety review, clinical decisions or professional biological analysis.
DNA sequence inputs are processed locally in the browser session by the calculator component and are not sent to an external biology API.
Frequently asked questions
What does the DNA Melting Temperature Calculator calculate?
DNA Melting Temperature Calculator answers use this tool for a quick dna melting-temperature estimate from base composition. It shows the model, substituted values, assumptions and a visual tied to the entered values.
What formula or model does the DNA Melting Temperature Calculator use?
DNA Melting Temperature Calculator uses Wallace rule: Tm ≈ 2(A + T) + 4(G + C) °C. Basic GC formula: Tm ≈ 64.9 + 41(G + C − 16.4)/length. The result breakdown shows how entered values feed the model.
What inputs are required for the DNA Melting Temperature Calculator?
Inputs for DNA Melting Temperature Calculator depend on the selected mode and are labelled in the calculator card. Required values are validated before a result appears.
How should I read the DNA Melting Temperature Calculator result?
DNA Melting Temperature Calculator uses deterministic TypeScript logic and local constants only.
How does the dynamic visual work on the DNA Melting Temperature Calculator?
The dynamic visual for DNA Melting Temperature Calculator is a DNA duplex with AT and GC melting contributions. It appears only after a valid calculation and includes the current result.
What assumptions does the DNA Melting Temperature Calculator make?
Important assumptions include: Only A, T, G and C are accepted. The selected empirical formula is appropriate for the intended screening use. The sequence is unmodified. These are shown in the page content.
What common mistakes should I avoid with the DNA Melting Temperature Calculator?
Common mistakes include Using ambiguous bases without an explicit rule. Treating a composition-only estimate as a complete primer-design result. Ignoring salt, magnesium, mismatches or secondary structure. Check units, model choice and input meaning before using the result.
What are the limitations of the DNA Melting Temperature Calculator?
Limitations include: Measured Tm depends on assay chemistry and sequence context. This tool does not model salt, magnesium, mismatches, dimers or hairpins. Use biological context and lab procedures for critical work.
Which related Biology calculator should I use next?
DNA Melting Temperature Calculator links to related Biology calculators so population, genetics and DNA-sequence workflows stay on canonical pages.
Is the DNA Melting Temperature Calculator safe for lab or privacy-sensitive use?
DNA Melting Temperature Calculator calculates locally from values entered in the browser session. It is for educational use and does not replace laboratory or professional guidance.
How is the DNA Melting Temperature Calculator different from adjacent Biology tools?
DNA Melting Temperature Calculator uses deterministic TypeScript logic and local constants only.
Can the DNA Melting Temperature Calculator be used for real experimental decisions?
DNA Melting Temperature Calculator uses deterministic TypeScript logic and local constants only.
References
- NCBI Bookshelf, Polymerase Chain Reaction. Relevance: PCR principles, reagents and amplification context. Last verified: July 28, 2026. Source.
- Bustin et al., MIQE Guidelines. Relevance: qPCR assay reporting and standard-curve quality. Last verified: July 28, 2026. Source.
- NCBI Bookshelf, Molecular Biology of the Cell. Relevance: DNA, enzymes and molecular-biology context. Last verified: July 28, 2026. Source.
Biology references and local calculation constants reviewed on July 28, 2026.
Educational disclaimer
This calculator provides mathematical results from the values, conventions and methods you enter. Verify important academic, engineering or professional work independently.