Calculate your solute in grams and your solvent in milliliters (mL). The w/v notation describes how to mix up a solution based on the solute and solvent measurements. For example, suppose you're told to dissolve 5 g of solute into a solvent to create a total volume of 200 mL.
Divide the weight by the volume: 5/200 = 0.025 g/mL.
Express the w/v result as a percentage. Multiply the number by 100 to get the percentage. In the case, 0.025 x 100 = 2.5 percent.
Express the answer in relation to the solute. In the example, suppose the solute was sodium chloride and you mixed it with 100 percent distilled water. You would describe the result as a 2.5 percent NaCl solution.
Keep in mind that you have to divide by the final volume of solute and the solvent together, instead of just the solvent. After a certain amount of solute is dissolved in solvent, volume increases. If you calculate w/v using only the solvent's volume, it will be wrong.