Preservative Challenge Calculator

Preservative system for target efficacy against microbes.

Batch size (g)

Water activity (aw)

Product pH

Preservative type (1-5)

Preservative level (%)

Rinse-off product? (0/1)

Tab to move between fields

Efficacy score (0-100)

Microbial risk (0-100)

Recommended level (%)1.08

Your preservative (g)10

Recommended amount (g)10.8

pH compatible? (1=yes)1

Concentration adequate? (1=yes)1

Over max limit? (1=yes)0

How to Use This Calculator

Enter the preservative active and its usage level percentage in the formula.
Set the product water activity (Aw) and pH.
Select target preservation standard (USP, EP, or cosmetic challenge test criteria).
Review the predicted preservation efficacy score.
Use the output to decide whether to increase preservative level or add chelating agents before challenge testing.

What each input means

Batch size (g): Total batch weight in grams.
Water activity (aw): Water activity of the product. Water = 1.0, anhydrous = <0.3. Products with aw > 0.6 need preservation.
Product pH: pH of the formulation. Lower pH generally aids preservation.
Preservative type (1-5): 1=Phenoxyethanol+EHG, 2=K-Sorbate+Na-Benzoate (pH<5.5), 3=MIT (rinse-off only), 4=BIT, 5=Organic acids (pH<5).
Preservative level (%): Your planned preservative concentration as a percentage of the batch.
Rinse-off product? (0/1): 0 = leave-on product (lotion, serum), 1 = rinse-off (shampoo, body wash).

Efficacy score (0-100): Estimated preservative efficacy. 80+ = good, 50-79 = marginal, <50 = inadequate.
Microbial risk (0-100): Product microbial contamination risk. Higher = more preservation needed.
Recommended level (%): Recommended preservative concentration based on risk assessment.
Your preservative (g): Grams of preservative at your specified concentration.
Recommended amount (g): Recommended grams of preservative for this batch.
pH compatible? (1=yes): Whether your product pH is within the effective range for this preservative.
Concentration adequate? (1=yes): Whether your concentration meets the minimum effective level.
Over max limit? (1=yes): Warning if concentration exceeds maximum allowed for this preservative.

Identify Input Parameters
4 parameters
Batch size (g) = 1000, Water activity (aw) = 0.85, Product pH = 5.5, Preservative type (1-5) = 1 = 6 input(s) provided
Calculate Efficacy score
Efficacy score
74 = 74
Calculate Microbial risk
Microbial risk = min(100, awRisk + phRisk + applicationRisk)
85 = 85
Calculate Recommended level
Recommended level = min(recommendedPct, maxAllowed)
1.08 = 1.08
Calculate Your preservative
Your preservative = batchSizeG * (preservativePct / 100)
10 = 10