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PCR Annealing Temperature Calculator

Biology
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This calculator determines the optimal annealing temperature for PCR based on primer sequences. The formula used is Tm = 2 * (A+T) + 4 * (G+C), where Tm is the melting temperature.

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How To Use

How to use this calculator

Start with your values, or try a preset.

Step 1

Enter Number of A (adenine) bases, Number of T (thymine) bases, Number of G (guanine) bases, and Number of C (cytosine) bases in the units shown.

Step 2

Read Melting Temperature (Tm) and Optimal Annealing Temperature in the results panel. Results update as you change the inputs.

Step 3

Choose a preset to load an example, then adjust the values for your situation.

Worked Examples

Example calculations

See the inputs and their calculated results.

Standard GC Content

Number of A (adenine) bases: 10; Number of T (thymine) bases: 10; Number of G (guanine) bases: 10; Number of C (cytosine) bases: 10

Melting Temperature (Tm): 120 °C; Optimal Annealing Temperature: 115 °C

High AT Content

Number of A (adenine) bases: 20; Number of T (thymine) bases: 20; Number of G (guanine) bases: 5; Number of C (cytosine) bases: 5

Melting Temperature (Tm): 120 °C; Optimal Annealing Temperature: 115 °C

High GC Content

Number of A (adenine) bases: 5; Number of T (thymine) bases: 5; Number of G (guanine) bases: 20; Number of C (cytosine) bases: 20

Melting Temperature (Tm): 180 °C; Optimal Annealing Temperature: 175 °C

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