PCR Primer Tm Calculator
Calculate melting temperature of PCR primers
About this calculator
The PCR Primer Tm Calculator determines the melting temperature (Tm) of DNA primers used in polymerase chain reaction (PCR) experiments. This tool is essential for molecular biologists and researchers as it helps optimize PCR conditions by ensuring primers have appropriate melting temperatures for efficient amplification. Proper Tm calculation prevents primer-dimer formation, improves specificity, and increases PCR success rates by enabling accurate annealing temperature selection.
How to use
Enter your primer DNA sequence into the input field using standard nucleotide letters (A, T, G, C). The calculator will automatically compute the melting temperature using established thermodynamic formulas. Use the calculated Tm to determine optimal annealing temperatures for your PCR protocol, typically 3-5°C below the Tm value.
Frequently asked questions
What is the ideal Tm range for PCR primers?
PCR primers should typically have Tm values between 50-65°C, with both forward and reverse primers having similar Tm values within 2-3°C of each other.
How does primer length affect melting temperature?
Longer primers generally have higher melting temperatures due to increased hydrogen bonding. Optimal primer length is usually 18-25 nucleotides for balanced specificity and stability.
What annealing temperature should I use based on Tm?
Set your PCR annealing temperature 3-5°C below the calculated Tm of your primers to ensure proper binding while maintaining specificity during amplification cycles.