Sequence Length Calculator
FREE TOOL
0 valid bases
Accepts both DNA (ATGC) and RNA (AUGC) — .txt, .fasta, .fa files supported
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BASE PAIRS (bp)
📊 Sequence Size Analysis
How to Use the Sequence Length Calculator
Step 1: Enter or paste your DNA or RNA sequence in the input box. The live counter updates as you type.
Step 2: Click Calculate Length for the full analysis including size comparison and molecular weight estimate.
Step 3: The tool automatically ignores spaces, numbers, line breaks and FASTA header lines — you get only the valid base count.
Sequence Length Reference Guide
Understanding sequence length is essential for experiment planning, primer design, gel electrophoresis and molecular weight calculations.
| Sequence Type | Typical Length | Example |
|---|---|---|
| PCR Primer | 18 — 25 bp | Standard primer length |
| Short oligonucleotide | 10 — 50 bp | Probe, siRNA |
| PCR product (small) | 100 — 500 bp | Standard PCR amplicon |
| PCR product (large) | 500 — 3000 bp | Long range PCR |
| Small gene | 500 — 2000 bp | Average gene coding sequence |
| Average human gene | ~27,000 bp | Including introns |
| Plasmid | 2,000 — 10,000 bp | Common cloning vector |
| Bacterial genome | 1 — 10 Mbp | E. coli ~4.6 Mbp |
| Human genome | ~3.2 Gbp | Per haploid set |