Ingredient Percentage Calculation: Weighing (grams) vs. Measuring (ml)
Question
I have questions regarding ingredient percentage calculation in cosmetic formulation, specifically concerning the difference between weighing (grams) and measuring volume (ml).
1. In the example "ต้องการใช้ 4กรัม นั่นคือ 57% ของ 5ml", how is the 57% calculated?
2. Does "การตวงว่าได้กี่ ml." mean weighing the ingredient that the store packed?
Answer
Hello!
It's understandable to find ingredient percentage calculations confusing at first, especially with the concepts of weighing and measuring volume involved. Based on the example you provided and the staff's clarification, here's an explanation:
Regarding the calculation of 57% in "ต้องการใช้ 4กรัม นั่นคือ 57% ของ 5ml":
- The 57% in this example does not come directly from a calculation between 4 grams and 5 ml. It likely refers back to the earlier information in the example stating that the product is packed in a 7-gram tube.
- The 57% calculation here probably means you want to use 4 grams of Vitamin B3 out of the total amount purchased, which is 7 grams.
- So, the calculation is (4 grams / 7 grams) * 100% ≈ 57.14%, rounded to 57%.
- The example then applied this 57% to the volume (5ml) obtained by measuring the 7-gram amount of Vitamin B3, in order to estimate the volume of 4 grams of Vitamin B3 (which resulted in 2.85ml).
- However, this method is an imprecise estimation because the weight (grams) and volume (ml) of most substances are not equal, except for pure water.
Regarding "การตวงว่าได้กี่ ml. คือการนำสารที่ทางร้านบรรจุมา มาชั่งน้ำหนักใช่มั้ยครับ":
- No, that's not correct. "การตวงว่าได้กี่ ml" means using a measuring cup or graduated cylinder marked in milliliters (ml) to measure the volume of the substance.
- "การชั่งน้ำหนัก" means using a scale to measure the weight of the substance in grams (g).
- As the staff explained, "ตวง" (measure volume) and "ชั่ง" (weigh) are different actions.
Summary and Further Advice:
Following the correct advice from the staff, to create accurate formulations and achieve desired results, you should always "weigh" all ingredients in "grams" and calculate percentages based on weight by weight (% by weight).
The correct and standard way to calculate ingredient percentage is:
(Weight of the ingredient (grams) / Total weight of the formula (grams)) * 100%
Using volume measurement instead of weighing is only a rough approximation when a high-precision scale is not available and can lead to inaccurate proportions.
I hope this explanation helps clarify the calculation method for you. If you have any more questions, feel free to ask!