Calculate the GC content (guanine-cytosine percentage) of a DNA sequence. GC content affects melting temperature and PCR primer design.
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Enter Your Measurements
Results
GC Content
44.0
%
Total Bases
420
bp
Estimated Tm (0.05M salt)
76.4
°C
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Formula
GC% = (G + C) / (A + T + G + C) × 100
How to Use This Calculator
How to Use
- 1
Count each base type in your sequence.
- 2
Enter the count for A, T, G, and C.
- 3
Get GC content and estimated melting temperature.
Frequently Asked Questions
Frequently Asked Questions
Why does GC content matter?
GC pairs have 3 hydrogen bonds vs 2 for AT pairs, making GC-rich DNA more thermally stable. This affects PCR primer Tm and hybridization conditions.
What is a good GC content for PCR primers?
Primers with 40–60% GC content are ideal. Extremes cause poor binding or hairpin formation.
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About This Calculator
This calculator uses the formula: GC% = (G + C) / (A + T + G + C) × 100. All calculations follow industry-standard methods. Results are estimates — always verify with a licensed professional for structural or code-compliant work.
Built and maintained by the CalcSmart team. Last updated March 2026.
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