GC Content Calculator
Calculate the GC percentage of any DNA or RNA sequence. Paste your sequence directly or enter base counts manually. Includes melting temperature (Tm) estimation and full base composition breakdown.
How GC Content Is Calculated
GC% = (G + C) / (A + T + G + C) × 100GC content is the percentage of guanine (G) and cytosine (C) bases in a DNA or RNA molecule, relative to the total number of bases. GC base pairs are held together by three hydrogen bonds (vs. two for AT pairs), making high-GC sequences more thermally stable — hence the correlation with melting temperature.
| Symbol | Variable | Description |
|---|---|---|
| G | Guanine count | Number of guanine nucleotides in the sequence. |
| C | Cytosine count | Number of cytosine nucleotides in the sequence. |
| A | Adenine count | Number of adenine nucleotides in the sequence. |
| T/U | Thymine / Uracil count | Thymine in DNA; Uracil in RNA sequences. |
How to Use This Calculator
- 1
Choose input method
Select 'Paste Sequence' to enter raw nucleotide sequences, or 'Enter Counts' to type in base numbers directly.
- 2
Paste or enter your data
For sequences, paste DNA/RNA text — spaces and numbers are ignored automatically. Mixed-case is accepted.
- 3
Click Calculate
GC%, AT%, total base count, and two Tm estimates appear instantly below the form.
- 4
Interpret Tm values
Use the Wallace rule Tm for short primers (14–20 bp). For longer sequences, the basic rule gives a rough approximation.
Frequently Asked Questions
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