About this tool
Paste a nucleotide sequence and choose a mode to convert between DNA and RNA. The input is sanitised — uppercased and stripped of anything that is not A, C, G, T or U — before it is processed, so spaces, numbers and FASTA line breaks are ignored. It all runs locally in your browser.
The coding-strand mode simply replaces every T with U, because the mRNA has the same sequence as the DNA coding (sense) strand. The template-strand mode complements each base using A↔T and G↔C and then replaces T with U, since mRNA is built antiparallel to the template. The RNA → DNA mode reverses transcription by replacing every U with T to give the DNA coding strand.
The result is shown as a copyable strand along with its length in nucleotides and the count of each base (A, C, G and combined T/U). For example, the coding strand ATGGCCTAA becomes the mRNA AUGGCCUAA.