Sequence basics

Length, base counts, GC content and reverse complement.

What this calculator does

Count the length and A, C, G and T bases of a DNA sequence, calculate its GC content and get the reverse complement, processed in your browser.

Base counting on strict A/C/G/T alphabet

F20 · Basic DNA sequence statistics: length = A + C + G + T; GC % = 100 · (G + C) / length; reverse complement: reverse, A↔T, C↔G

GC content is not a melting-temperature estimate.
tests-passed means automated algorithm tests (unit, property, integration and browser end-to-end) pass. It is not an independent scientific review and not laboratory validation.

[S07] Biopython: Bio.SeqUtils.MeltingTemp documentation/source (accessed 2026-10-29)
[S08] IDT: OligoAnalyzer (accessed 2026-10-29)

The calculator runs in your browser and needs JavaScript. Your inputs are processed locally.

Stock dilution: Stock and diluent volumes from C₁V₁ = C₂V₂.
Serial dilution: Dilution series with per-tube volumes and concentrations.
dsDNA mass & molarity: ng ↔ pmol, ng/µL ↔ nM, copy number, mass ↔ volume.
PCR master mix: Per-reaction and batch volumes, custom or kit example preset.
Primer volume: Forward and reverse primer stock volumes per reaction.
DNA ligation: Insert mass and pipetting volumes for an insert:vector molar ratio.
Molarity & mass: Mass, concentration, volume or amount from molecular weight.
Reaction / master mix: Generic reaction setup with water to volume and batch scaling.