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DNA Calculator

Complement, reverse complement, GC% and base composition for a DNA sequence.

Introduction

DNA Calculator — Complement, reverse complement, GC% and base composition for a DNA sequence. Enter DNA sequence to get an instant, accurate result.

Formula

Watson-Crick base pairing: A pairs with T, C pairs with G. The complement strand substitutes each base with its pair; the reverse complement additionally reverses the strand order (5′→3′ of the opposite strand). GC content % = (G+C count / total length) × 100.

Step-by-step

  1. Enter the DNA sequence.
  2. Click Calculate to see your result instantly.

Real-world example

Example: With DNA sequence = ATGCATGCTAGC, the DNA Calculator gives Length: 12, Complement: TACGTACGATCG, Reverse Complement: GCTAGCATGCAT.

Frequently Asked Questions

What is the difference between the complement and the reverse complement?
The complement simply swaps each base for its pair (A↔T, C↔G) in the same left-to-right order you entered. The reverse complement also reverses that order, which is what actually represents the opposite strand read 5′ to 3′ — the form used in most lab and bioinformatics work.
Why do only A, C, G, T count?
Any character that is not a valid DNA base letter is stripped out before counting, so spaces, line breaks, or ambiguity codes (like N) are ignored rather than treated as a fifth base.
What does the GC percentage tell me?
Since G-C pairs are held together by three hydrogen bonds versus two for A-T, a higher GC% generally means a more thermally stable double helix.
What inputs does the DNA Calculator need?
You'll need to provide: DNA sequence. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the DNA Calculator?
The DNA Calculator applies the formula exactly as calculated — Watson-Crick base pairing: A pairs with T, C pairs with G. The complement strand substitutes each base with its pair; the reverse complement additionally reverses the strand order (5′→3′ of the opposite strand). GC content % = (G+C count / total length) × 100. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the DNA Calculator free to use?
Yes, the DNA Calculator is completely free, requires no signup, and runs instantly in your browser.

About the DNA Calculator

The DNA Calculator uses a real, verifiable formula — Watson-Crick base pairing: A pairs with T, C pairs with G. The complement strand substitutes each base with its pair; the reverse complement additionally reverses the strand order (5′→3′ of the opposite strand). GC content % = (G+C count / total length) × 100. — so results are accurate every time, not an approximation.