Working out a Percentage

Introduction

Generally speaking, most ingredient amounts are calculated or expressed as a percentage of a batch by weight. To work out a percentage, take the size of your batch (in pounds, weight ounces or grams) and multiply by the percentage required. For example if you are making a 5 lb. batch of cream and need to add 2% of an essential oil, you should first convert 5 lbs. to 80 oz. ( 5lbs. x 16 oz. = 80 oz.) and then multiply 80 oz. by .02 (2%) which gives you 1.6 oz. If the resulting number is very small, you can convert it to grams for easier, more accurate weighing. 1 oz. = 28.35 grams so 1.6 oz. x 28.35 grams = 45.36 grams. You can then use a gram scale for measuring out 45.36 grams accurately.

Occasionally, people add an ingredient as a percentage of a batch by volume instead of weight. In this case, take the volume of your batch and multiply by the percentage to get the volume of the ingredient to use. For example, if you are making a 64 oz. batch of lotion and you want to use 1% by volume of essential oil, you would multiply 64 oz. by .01 (1 %). This gives you .64 oz.

If the resulting number is very small or difficult to measure and you are working in volumetric ounces, you can multiply the number of ounces by 30 to get the total number of milliliters (or cc). 64 oz. x .01 (1%) x 30 = 19.2 ml or 19.2 cc. You can usually find ml/cc syringes at pharmacies. You can find pipettes within our equipment section.