Reverse Complement Calculator
Paste a DNA or RNA sequence to get its reverse complement, complement, or reverse. IUPAC ambiguity codes are handled and FASTA headers, spaces and numbers are ignored.
Paste a sequence above to see the result.
How it works
The complement of a DNA strand pairs each base with its Watson–Crick partner: A with T, G with C (and A with U in RNA). The reverse complement reverses that complemented strand, giving the sequence you would read on the opposite strand in the 5′→3′ direction — exactly what you need when designing a reverse primer or interpreting the antisense strand.
Paste a sequence and choose reverse complement, complement only, or reverse only. IUPAC ambiguity codes (R, Y, N and the rest) are complemented correctly, and anything that is not a letter — FASTA headers, line breaks, spaces, position numbers — is stripped before processing. Tick RNA output to write the result with U instead of T.
Examples
- ATGC → reverse complement → GCAT.
- 5′-ATGCTAGC-3′ → reverse complement → GCTAGCAT (the reverse-strand primer).
- Ambiguity codes: R (A/G) complements to Y (C/T).
Frequently asked questions
- What is a reverse complement?
- It is the sequence of the opposite DNA strand read 5′→3′. You complement each base (A↔T, G↔C) and then reverse the order.
- Does it handle RNA?
- Yes. Tick RNA output and the result is written with U in place of T. U in the input is treated as equivalent to T.
- What about ambiguity codes?
- All IUPAC nucleotide codes are supported and complemented correctly, for example R (purine) becomes Y (pyrimidine) and N stays N.
- Can I paste FASTA?
- Yes. Lines beginning with > are ignored, and whitespace and numbers are removed automatically, so you can paste straight from a FASTA file.