Enter a DNA or RNA sequence into the calculator to determine the percentage of each nucleotide (A, T/U, C, G), along with GC content (and AT/AU content). You can also generate a DNA reverse complement and compute GC% across a sequence using a sliding window.

DNA Percentage Calculator

DNA Composition RNA Composition Reverse Complement GC Content (Window)

Percentage of Nucleotides:

Related Calculators

DNA Nucleotide Percentage Formula

The following formulas are used to calculate nucleotide percentages (base composition) within a single DNA (or RNA) sequence.

\%X = (N_X / N_{total}) * 100

Common composition summaries:

\%GC = ((N_G + N_C) / N_{total}) * 100

For DNA, AT content is:

\%AT = ((N_A + N_T) / N_{total}) * 100

For RNA, AU content is:

\%AU = ((N_A + N_U) / N_{total}) * 100

Variables:

  • %X is the percentage of a specific nucleotide X (A, T/U, C, or G) (%)
  • NX is the count of nucleotide X in the sequence
  • Ntotal is the total number of nucleotides in the sequence (sequence length, in nt)

To calculate a nucleotide percentage, divide the count of that nucleotide by the total sequence length, then multiply by 100. GC%, AT%, and AU% are calculated the same way using the combined counts.

What is a DNA Percentage?

On this page, “DNA percentage” refers to base composition: the percentage of each nucleotide (A, T, C, and G) present in a DNA sequence, along with summary measures like GC content (G+C) and AT content (A+T). These percentages describe a sequence itself (or windows within a sequence), not how much DNA two people share. Shared-DNA percentages used in ancestry/relationship testing come from population genetics methods and are a different concept.

How to Calculate DNA Percentage?

The following steps outline how to calculate nucleotide percentages (base composition) for a DNA sequence.

  1. Write down the DNA sequence and remove any spaces or line breaks.
  2. Count how many A, T, C, and G bases are present.
  3. Compute the total length Ntotal (in nucleotides, nt).
  4. Calculate each nucleotide percentage using %X = (NX / Ntotal) × 100.
  5. Optionally compute GC% = ((NG + NC) / Ntotal) × 100 and AT% = ((NA + NT) / Ntotal) × 100.

Example Problem:

Use the following variables as an example problem to test your knowledge.

DNA sequence = ATGCGCATTAACGTTAGC (18 nt)

A = 5 (27.78%), T = 5 (27.78%), C = 4 (22.22%), G = 4 (22.22%), GC% = 44.44%