Calculating Ingredient Percentages in Formulation

Subject: How to calculate ingredient amounts?

Hello! You're asking how to calculate the amount of chemicals and preservatives to add to your 800g water+oil base, based on percentages. This is a common calculation in cosmetic formulation.

Here's how to think about it and calculate the amounts:

1. Percentages are based on the Total Weight: In formulation, percentages (%) always refer to the proportion of an ingredient relative to the final total weight of the entire batch.
   Formula: Amount of Ingredient (g) = (Percentage of Ingredient / 100) * Total Weight of Formulation (g)

2. Your 800g is Part of the Total: You have 800g of water and oil. This 800g is not the total weight of your final product; it's just the weight of your water and oil phase. You will add other ingredients (chemicals, preservatives, etc.) to this base, which will increase the total weight.

3. How to Calculate When You Have a Base Weight: Since you have a fixed base of 800g (water + oil), and you want to add other ingredients based on their percentage of the final total, you need to calculate the final total weight first.

   Let's say you want to add:

   • Preservative at P_preservative % of the total weight
   • Chemical at P_chemical % of the total weight
   • (Add percentages for any other ingredients you plan to add)

   Let the total percentage of all ingredients you plan to add to the 800g base be P_added_total = P_preservative + P_chemical + ...

   Your 800g of water and oil represents the remaining percentage of the total formulation: 100% - P_added_total %.

   So, 800g corresponds to (100 - P_added_total) / 100 of the total weight (let's call the total weight 'T').
   800g = ((100 - P_added_total) / 100) * T

   To find the total weight (T), rearrange the formula:
   T = 800g / ((100 - P_added_total) / 100)
T = 800g * 100 / (100 - P_added_total)

   Once you have the Total Weight (T), you can calculate the amount of each ingredient you want to add:
   Amount of Preservative (g) = (P_preservative / 100) * T
Amount of Chemical (g) = (P_chemical / 100) * T
(Calculate amounts for any other added ingredients similarly)

4. Example Calculation:
   Let's assume you want to add:

   • Preservative at 1% of the total weight
   • Chemical at 5% of the total weight

   • (No other ingredients for this example)

   • Total percentage of added ingredients (P_added_total) = 1% + 5% = 6%.

   • The 800g water+oil base represents 100% - 6% = 94% of the total weight.

   • Calculate the Total Weight (T):
     T = 800g * 100 / (100 - 6)
T = 800g * 100 / 94
T ≈ 851.06 g (This is your target final batch size)

   • Calculate the amount of Preservative to add:
     Amount of Preservative = (1 / 100) * 851.06g ≈ 8.51 g

   • Calculate the amount of Chemical to add:
     Amount of Chemical = (5 / 100) * 851.06g ≈ 42.55 g

   • Check: 800g (Water+Oil) + 8.51g (Preservative) + 42.55g (Chemical) ≈ 851.06g (Total). The numbers should add up to the calculated total weight (T).

5. Important Notes:

   • The percentage to use for each chemical or preservative depends on the specific ingredient and its recommended usage rate. Always check the supplier's documentation or product information for the correct percentage range.
   • Make sure to weigh all ingredients accurately using a scale.

I hope this explanation helps you understand how to calculate the amounts! You just need to decide on the percentage you want for your chemical(s) and preservative(s), plug those percentages into the formula to find the total weight, and then calculate the amount for each ingredient.