Tm calculator is a tool to estimate primer pair for melting temperature. It can be opened from menu Tools>Tm Calc. To estimate melting temperature enter sequences of both primers to the text fields. Context menu item "Paste" can be used as well. To calculate Tm of primers press button "Calculate". Melting temperature will appear under both of primer text field. "Tm of two primers" shows the temperature recommended for PCR with there oligonucleotides (minimal Tm of two primers minus 5°C). Tm is estimated as Tm="Number of G/C"*4+"Number of A/T"*2.