GC Content
Proportion of G and C bases in DNA.
Formula
Live Calculator
MembersVariables
How it works
GC content tells you what fraction of the bases in a DNA sequence are guanine (G) or cytosine (C). The formula works because it compares the number of G and C bases to the total number of bases in the sequence, then converts that fraction into a percentage. Since DNA sequences are made up of A, T, G, and C, adding all four counts gives the sequence length.
When to use it
Use this when analyzing DNA sequences in genetics, genomics, or bioinformatics, especially to compare regions or species. It is also useful for checking whether a sequence may be unusually GC-rich or GC-poor, which can affect DNA stability and gene prediction.
Worked example, step by step
Suppose a DNA segment contains 12 A bases, 8 T bases, 15 G bases, and 5 C bases. Step 1: Add the G and C bases: 15 + 5 = 20 Step 2: Add all bases: 12 + 8 + 15 + 5 = 40 Step 3: Divide GC by total bases: 20 / 40 = 0.5 Step 4: Convert to a percentage: 0.5 × 100 = 50% Final answer: %GC = 50%
Common mistakes to avoid
- Using only the number of G bases or only the number of C bases instead of both together
- Forgetting to include all four base counts in the total sequence length
- Writing the result as a decimal like 0.5 without converting it to a percentage
Did You Know?
DNA rich in G-C pairs is more heat-stable, since those pairs share three hydrogen bonds instead of two.
Share this formula
More in Biology & Life Sciences
View allHardy-Weinberg Equilibrium
IntermediateGenotype frequencies in a non-evolving population.
Allele Frequency Sum
BasicThe two allele frequencies must total 1.
Exponential Population Growth
IntermediateUnlimited growth of a population over time.
Logistic Growth
AdvancedPopulation growth limited by carrying capacity.
Per Capita Growth Rate
BasicNet growth rate from birth and death rates.
Population Doubling Time
IntermediateTime for a population to double.