DNA/RNA molarity Calculator:
  M = w / MW
Where:
M: DNA molarity, in mol
w: DNA weight, in g
MW: DNA molecular weight, in g/mol

If only DNA length is given, the molecular weight is calculated as:
MW = DNA Length (bp) × DNA/RNA base weight
The approx. double strand DNA base weight is 650 Dalton, for single strand is 330, for RNA is 340 Dalton.