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Primer Tm calculator
Paste a PCR primer and get its melting temperature by two standard estimates, its GC content, and a quick quality check — length, 3′ GC clamp and long single-base runs.
0 bases · Spaces, line numbers and FASTA headers are removed automatically.
Primer check
Good to know
Which Tm should you trust?
The Wallace rule (2 °C per A/T, 4 °C per G/C) suits short primers under ~14 nt. For longer primers the salt-adjusted estimate is the better guide, and nearest-neighbour calculators (like your thermocycler software) refine it further with salt and primer concentrations. Design primer pairs within ~2 °C of each other.