Molarity refers to the molar concentration of a solution, that is, the number of moles of solute dissolved in 1 liter of solution, as mol/L, abbreviated as M.

Molarity Calculator Equation:
   Molarity = Mass / (Volume × Molar Mass);
   Mole = Concentration (g/L) × Volume (L) / MW (g/mol);

Molarity Calculation Example:
(1) Calculate moles of a 15ml NaCl solution with concentration 0.2g/L
     The molar mass of NaCl is 58.44276 g/mol (Click here for molar mass calculator).      So:
     mole = 0.2 * (15 / 1000) / 58.44276 = 0.000051332278 (mol)

(2) What's the mass of NaCl required to make a 0.2mol/L solution in 15ml of water?
     The molar mass of NaCl is 58.44276 g/mol.
     So:
     Mass = 0.2 * (15 / 1000) * 58.44276 = 0.175328 (gram)