Melting Temperature Calculator
Calculate DNA melting temperature (Tm) using multiple methods for accurate PCR primer design.
Primer Sequence
Calculation Methods
Basic (Wallace): Tm = 2(A+T) + 4(G+C)
Salt-adjusted: Accounts for ionic strength
Nearest-neighbor: Most accurate for primers
Recommended Tm
49.2°C
Salt-adjusted method | GC: 52.4%
Tm by Different Methods
Basic (Wallace Rule)64.0°C
Best for oligos under 14 bp
Salt-Adjusted49.2°C
Recommended for typical PCR primers
Nearest-Neighbor (approx)80.1°C
Thermodynamic calculation
GC-Adjusted54.4°C
PCR Recommendations
Annealing Temperature44.2°C
Tm - 5°C (typical starting point)
Extension Temperature72°C
Standard for Taq polymerase
Primer Properties
Length
21 bp
GC Content
52.4%
G + C
11
A + T
10
Quality Assessment
✓Length: Optimal (18-25 bp)
✓GC%: Optimal (40-60%)
!Tm: Consider adjusting