Reverse Complement Generator
Generate the reverse complement of DNA, including IUPAC ambiguity codes.
Your result, clearly explained
Paste a sequence or load the example, then run the tool. Your sequence stays in this browser.
How to use
- Paste a DNA strand
Use a sequence written 5′→3′, with optional FASTA header.
- Generate the opposite strand
The tool complements each base and reverses the sequence.
- Copy the result
Use the resulting 5′→3′ strand in your next analysis.
Why ToolerWork?
Sequence calculations run inside your browser.
Strand direction, code table and approximation limits are explained.
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Why use this tool?
- Handle both canonical and ambiguous IUPAC DNA bases.
- Keep the opposite strand in the conventional 5′→3′ direction.
- Avoid manual base substitution and reversal errors.
Method & assumptions
The base pairs are A↔T and C↔G. Ambiguity complements are R↔Y, K↔M, B↔V and D↔H; S, W and N stay unchanged. Complemented bases are returned in reverse order.
References: NCBI genetic codes
Explore all 10 biology tools →Frequently asked questions
What is the difference between complement and reverse complement?
A complement swaps paired bases without changing order. A reverse complement also reverses the order, so the opposite strand can be written 5′→3′.
Can I enter lowercase DNA?
Yes. Lowercase letters become uppercase and whitespace is removed before processing.
What happens to R, Y and N?
R and Y swap because purines complement pyrimidines. N represents any base and remains N. Other IUPAC ambiguity pairs are also supported.
Will reversing the result again restore my input?
Applying reverse complement twice restores a valid DNA sequence, apart from normalization of letter case and whitespace.
Does this tool design a reverse primer?
It can supply a reverse-complement sequence, but primer design also needs melting temperature, specificity and secondary-structure checks that this tool does not perform.