DIY Beauty Calculators
Preservative amount.
Enter your batch weight and pick a preservative to get the grams to weigh out, the range the source states, and the temperature to stay under when you add it. Only water-containing products need one. Runs in your browser; nothing is sent or stored.
Batch and preservative
Your preservative
Fill the form and press Calculate.
Worked example
For a 200 g batch: Liquid Germall Plus at 0.5% is 1.00 g; Geogard ECT at its 1.0% maximum is 2.00 g (range 1.20 to 2.00 g); Optiphen Plus at its 1.5% maximum is 3.00 g (range 1.50 to 3.00 g). Preservative grams = batch grams x usage rate / 100, so 200 x 1.0 / 100 = 2.00.
How it works
The tool only does the percentage arithmetic. The ranges are what the sources state: Humblebee & Me gives 0.1 to 0.5% for Liquid Germall Plus, uses 0.5%, and says to add it below 50 C (122 F) once the product has cooled; Voyageur Soap & Candle lists Geogard ECT at 0.6 to 1.0% with pH 3.0 to 8.0, added below 45 C in emulsions, and Optiphen Plus at 0.75 to 1.5%, which can go in at 80 C or below. The Liquid Germall Plus default is 0.5%, the top of its range, because Humblebee & Me says home labs are not sterile, so it is best to err on the side of more, but never above the maximum (that advice is Humblebee & Me's for Germall only). The Geogard ECT (1.0%) and Optiphen Plus (1.5%) defaults are the supplier maximums from Voyageur, chosen here as a conservative home-lab default.
A usage rate is only part of preservation. Check the effective pH range, solubility and any incompatibilities for your formula. Humblebee & Me states that water always means a preservative is needed unless the product is for immediate use, that natural-sounding ingredients such as sodium lactate, grapefruit seed extract and rosemary are not preservatives, and that antioxidants like vitamin E do not preserve a water-containing product.
Sources (opened 2026-10-08): Humblebee & Me, FAQ; Humblebee & Me, Super Simple Moisturizing Lotion; Voyageur Soap & Candle, Geogard ECT Preservative; Voyageur Soap & Candle, Optiphen Plus Preservative.
FAQ
How much preservative do I put in lotion?
Use the rate on your supplier data sheet. Liquid Germall Plus is 0.1 to 0.5% (0.5% in the Humblebee & Me lotion), Geogard ECT is 0.6 to 1.0%, and Optiphen Plus is 0.75 to 1.5%, as stated by the sources on this page.
What products need a preservative?
Humblebee & Me says anything containing water, including lotions, needs a broad-spectrum preservative unless it is made for immediate use. Water-free products such as lip balm and lotion bars should not, if kept dry.
Is vitamin E or grapefruit seed extract a preservative?
No. Humblebee & Me says antioxidants and ingredients such as grapefruit seed extract, rosemary and sodium lactate are not stand-alone preservatives for a product with water.
When do I add the preservative?
In the cool-down phase, below the product heat limit: under 50 C for Liquid Germall Plus, under 45 C for Geogard ECT in an emulsion, and at 80 C or below for Optiphen Plus. Humblebee & Me says most go in below 40 C.
How long does lotion last without a preservative?
Humblebee & Me says it cannot give a shelf-life estimate for anything with water, and that such products are probably only good for a day or two without a broad-spectrum preservative.
Disclaimer
Not medical or safety advice. This tool does not test whether your product is preserved. Too little preservative can let bacteria and mould grow, and too much can irritate skin. Use the supplier data sheet for your exact product, formula and pH, weigh on an accurate scale, and discard products that change colour, smell or texture. A homemade product to sell needs professional safety testing.