welcome back in the last video we learned how to calculate the quantity to dispense now we'll focus on calculating the quantity of an ingredient in a compounded preparation this is essential for ensuring accurate and safe medication preparations to calculate the quantity of an ingredient we need to know the dose and the strength of the medication we'll use a ratio or proportion equation to solve for the unknown quantity let's go through an example to understand this better here's a problem a prescription calls for a medication that contains 0.25% of a specific active ingredient the patient requires a total of 500 milliliters of the medication how many milligrams of the active ingredient should be present in the entire 500 milliliters to solve this follow these Steps step one convert the percentage to a decimal you can always do this by dividing the percentage by 100 so25 / 100 = 0.25 step two multiply the total volume by the decimal to find the quantity of the ingredient quantity of ingredient equals 500 mill * 0.0025 which equals 1.25 G step three convert grams to milligrams if needed as you may recall to convert gram to milligram we multiply G by 1,000 so we have 1.25 G equal 1,250 mg so 1,250 mg of the active ingredient should be present in the entire 500 mL let's practice another problem together a prescription calls for a medication that contains 1% of a specific active ingredient the patient requires a total of 200 milliliters of the medication how many milligrams of the active ingredient should be present in the entire 200 M step one convert the percentage to a decimal 1% equals to 0.01 step two multiply the total volume by the decimal to find the quantity of the ingredient quantity of ingredient equals to 200 Mill * 01 equal 2 G step three convert gr to milligrams if needed 2 G equal 2000 mg so 2,000 mg of the ingredient should be present in the entire 200 mL now it's your turn to try a problem on your own a prescription calls for a medication that contains 0.5% of a specific active ingredient the patient requires a total of 100 milliliters of the medication how many milligrams of the active ingredient should be present in the entire 100 mlit pause the video solve the problem and then we'll check the answer together let's see how you did step one convert the percentage to a decimal 0.5% equal 0.005 step two multiply the total volume by the decimal to find the quantity of the ingredient quantity of ingredient equals 100 Mill * 0.005 = 05 G step three convert G to milligrams if needed we have 0.5 G equal 500 mg so 500 mg of the active ingredient should be present in the entire 100 ml great job you've now learned how to calculate the quantity of an ingredient in the next video we'll cover how to calculate the day supply