Calculating Preservative Weight by Percentage

To calculate the weight of a preservative, such as Phenoxyethanol, needed for your formula based on a percentage, you can use a simple formula.

The basic calculation is:

Weight of Ingredient (grams) = (Desired Percentage / 100) * Total Weight of the Formula (grams)

For example, if you want to add Phenoxyethanol at 1% to a 100-gram formula:

Weight of Phenoxyethanol = (1 / 100) * 100g = 1 gram

If your formula is 50 grams and you want to add Phenoxyethanol at 1%:

Weight of Phenoxyethanol = (1 / 100) * 50g = 0.5 grams

As the staff mentioned, for beginners, calculating 1% of the total formula weight is generally recommended for reliable preservation.

For more experienced formulators, or in formulas with a high water content, you might consider calculating the percentage based on the water phase weight. If your 100-gram formula contains 60 grams of water and you decide to add Phenoxyethanol at 1% of the water phase:

Weight of Phenoxyethanol = (1 / 100) * 60g = 0.6 grams

This is why you might see different percentages used in different formulas – it depends on the total formula size and sometimes the specific calculation method (total formula vs. water phase) chosen by the formulator.

Remember that the appropriate percentage can also depend on the specific type of Phenoxyethanol or preservative blend used (like Phenoxyethanol SA or Chlorphenesin / Phenoxyethanol) and the nature of the formula itself (e.g., high natural content, high water content). Always refer to the recommended usage rate for the specific preservative product you are using.

For safety and effectiveness, especially when starting out, using 1% of the total formula weight is a good standard practice.

Relevant products mentioned:

• Phenoxyethanol (Extra Pure)
• Phenoxyethanol SA (eq. Optiphen Plus)
• Chlorphenesin / Phenoxyethanol (Microcare PHC eq.)
• Phenoxyethanol P5