Biology
Annealing Temperature (Tm) Calculator
Lets users compute and verify annealing temperature (tm) instantly with formula, steps and examples — no manual math.
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Your result
Melting temperature (Tm)
47.68 °C
Primer Tm ≈ 47.7 °C (40% GC, 20 bases). Anneal ~3–5°C below Tm.
GC content
40%
Primer length
20 bases
About this calculator
PCR primer Tm: for short primers (<14 nt), Tm = 2(A+T) + 4(G+C) (Wallace rule); longer primers use the GC% formula. Annealing temperature is set ~3–5°C below Tm.
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