Calculate the melting temperature (Tm) of your oligonucleotide sequence.
About Tm Calculation
The melting temperature (Tm) is the temperature at which half of the DNA duplexes dissociate into single strands. This calculator supports two methods:
- Wallace Rule:
Tm = 2(A+T) + 4(G+C)— quick estimation for short oligos (<20 nt) - Nearest-Neighbor (SantaLucia 1998): Uses thermodynamic nearest-neighbor parameters, with corrections for salt (Na⁺) and Mg²⁺ concentrations, dNTPs, and oligo concentration. This is the most accurate method for longer oligos.
Additional features include:
- Molecular Weight and Extinction Coefficient calculation from sequence composition
- Self-complementarity / Dimer check — detects potential 3’-end homodimer formation
- Hairpin prediction — detects potential self-loop structures
- Mg²⁺ correction using the von Ahsen (2001) method, accounting for dNTP chelation of free Mg²⁺
- Sequence validation — strips invalid IUPAC characters with a warning
