Tm Calculator
Calculate DNA melting temperature for primers and oligonucleotides.
Primer Sequence
Enter A, T, G, C only (other characters ignored)
Melting Temperature (Tm)
29.7C
Annealing: 24.7C (Tm - 5)
Sequence Properties
Length20 bp
GC Content50.0%
Molecular Weight6117 Da
Base Composition
A
5
T
5
G
5
C
5
PCR Guidelines
Optimal primer length: 18-25 bp
Optimal GC content: 40-60%
Optimal Tm: 55-65C
Primer pair Tm difference: max 5C
3' end: End with G or C (GC clamp)
💡
Help us improve!
How would you rate the Tm Calculator?
Editorial Note
MyCalcBuddy Editorial Team
This page is maintained as an educational calculator reference.
📚
Formula Source: Standard Mathematical References
by Various
🔄Last reviewed: May 2026
✓Formula checks are based on standard references and internal QA review.