Reverse Complement Calculator

🪞 Reverse Complement Calculator FREE TOOL

Enter DNA or RNA Sequence (5'→3') *

0 characters

Sequence Type Mode

Output Style

📂 Upload File

Accepts .txt, .fasta, .fa files — FASTA headers removed automatically

Original Sequence (5'→3')

Complement (3'→5')

Reverse Sequence (3'→5')

✅ Reverse Complement (5'→3')

How to Use the Reverse Complement Calculator

Step 1: Enter your DNA sequence in the 5' to 3' direction in the input box above.

Step 2: Click Calculate. The tool shows you four results — original sequence, complement, reverse and reverse complement.

Step 3: The Reverse Complement (shown in green) is the most commonly needed result for primer design.

Step 4: Use the individual Copy buttons to copy any specific result.

How Reverse Complement Works

The reverse complement is essential in molecular biology because DNA is double stranded. When designing a reverse primer you need the reverse complement of the target sequence.

// Step 1 — Complementary base pairing rules:
A ↔ T
T ↔ A
G ↔ C
C ↔ G

// Step 2 — Reverse the complement sequence
Original 5'→3' : ATGCTA
Complement 3'→5': TACGAT
Rev Complement 5'→3': TAGCAT

Worked Example

Input — Original Sequence (5'→3')

5' — A T G C T A G C — 3'

↓ Step 1 — Get complement (A↔T, G↔C)

3' — T A C G A T C G — 5'

↓ Step 2 — Reverse it (read 5'→3')

Output — Reverse Complement (5'→3')

5' — G C T A G C A T — 3'

When Do You Need Reverse Complement?

You need the reverse complement when designing reverse primers for PCR. The reverse primer binds to the bottom strand of DNA which runs in the opposite direction. The reverse complement of your target gives you the sequence of the reverse primer.

How to Use the Reverse Complement Calculator

How Reverse Complement Works

Worked Example

When Do You Need Reverse Complement?

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