DNA GC Content Calculator
What is this tool?
This free online GC content calculator analyzes DNA sequences to compute GC percentage, AT/GC ratio, molecular weight, and estimated melting temperature. It is built for molecular biologists, geneticists, and bioinformaticians working with DNA sequence analysis.
Calculate GC content, base composition, molecular weight, and estimated melting temperature for any DNA sequence. Essential for PCR primer design and probe development.
Last updated: July 2026 · Reviewed by VigyanLLM Research Team
VigyanLLM's GC content calculator analyzes DNA and RNA sequences to determine GC composition, Tm, and sequence length. Optimal GC content (40-60%) is critical for primer design, as extreme values lead to secondary structures and failed PCR amplification.
| Metric | Analysis |
|---|---|
| GC Percentage | Ratio of G+C bases to total bases |
| AT Content | Complementary A+T base pair percentage |
| Sequence Length | Total nucleotide count |
| Melting Temperature | Estimated using nearest-neighbor formula |
Enter a DNA Sequence
| Parameter | Value |
|---|---|
| Sequence Length | — |
| Adenine (A) | — |
| Thymine (T) | — |
| Guanine (G) | — |
| Cytosine (C) | — |
| GC Content | — |
| AT/GC Ratio | — |
| Molecular Weight | — |
| Estimated Tm (basic) | — |
What Is GC Content?
GC content is the percentage of guanine (G) and cytosine (C) bases in a DNA sequence. Since G-C pairs form three hydrogen bonds (vs. two for A-T), higher GC content increases DNA stability and melting temperature.
Why Is GC Content Important?
- PCR primer design — optimal GC content is 40–60%
- Melting temperature — higher GC = higher Tm
- Genome stability — GC-rich regions are more thermostable
- Gene expression — GC content affects transcription and translation efficiency
- Probe design — TaqMan probes need controlled GC content for specificity
GC Content Reference Values
- Human genome: ~41%
- E. coli genome: ~51%
- Mouse genome: ~42%
- SARS-CoV-2 genome: ~38%
- Optimal PCR primers: 40–60%
Related Tools
- Primer Tm Calculator — accurate Tm using nearest-neighbour thermodynamics
- AI Primer Design Tool — design validated primer pairs
- PCR Analysis Software — full PCR setup and simulation
Frequently Asked Questions About GC Content Calculator
Everything you need to know about using this tool
Is the GC Calculator free to use?
Yes, the GC Content Calculator is completely free with no usage limits. No login, account, or API key required. All calculations happen in your browser.
What is GC content?
GC content is the percentage of guanine (G) and cytosine (C) bases in a DNA sequence, calculated as (G+C)/(A+T+G+C) × 100%. It is a key metric in molecular biology.
Why is GC content important for PCR?
GC content affects primer stability, melting temperature, and PCR efficiency. A GC content of 40–60% is typically ideal for primers. Extreme GC content may require adjusted PCR conditions.
What does this tool calculate?
The calculator shows GC percentage, AT/GC ratio, base composition (A/T/G/C counts), molecular weight, and estimated melting temperature for any entered DNA sequence.
What sequence formats are accepted?
You can paste raw DNA sequences or FASTA-formatted sequences. Non-DNA characters are automatically filtered out, and the tool also supports file upload.
Is my sequence data stored or shared?
No. All calculations run entirely in your browser. Sequences are never sent to any server, stored, or shared.