Lotions · creams · balms
Lotion Formula Calculator
Lay out a formula by phase, make it add up to exactly 100 % and turn it into grams for the batch you want to make, with your supplier's usage rates checked as you go.
Anything made with water needs a broad-spectrum preservative, one that covers bacteria, yeast and mould, at your supplier's usage rate. Emulsifier and preservative amounts always come from your supplier's data sheet, never from a calculator.
How to use the lotion calculator
Set the batch size first, in grams, ounces or pounds. Then give every ingredient its own row with its phase and its percentage of the finished product. The phases follow the order most lotions are made in: the water phase and the oil phase are heated separately, the emulsifier usually melts in with the oils, and the cool-down phase is stirred in once the emulsion has cooled.
The percentages must add up to exactly 100 %. Tick Balance on one row, normally the water, and that row takes whatever is left; the bar above the table shows how close you are.
For the emulsifier and the preservative, type the usage range from your supplier's data sheet into the two rate boxes. The calculator never suggests a rate: use your supplier's rate, and it flags anything below the minimum or above the maximum. It also warns when a formula contains water but no preservative, or water and oil but no emulsifier.
Worked example
The example layout makes 200 g. Glycerin at 3 % is 200 × 3 ÷ 100 = 6 g. The oil phase adds up to 18 %, so 36 g, and with every other row fixed the balance row gives the water 72.5 %, or 145 g. Double the batch to 400 g and every weight doubles while the percentages stay the same. The example only shows how a formula is laid out: its emulsifier and preservative figures are placeholders until you enter your supplier's rates.
Copy the result, download it as a CSV file for a spreadsheet, or print it for the workbench.
What goes in each phase
- Water phase: distilled water, hydrosols, glycerin and other water-soluble ingredients.
- Oil phase: liquid oils, butters and thickeners such as fatty alcohols (cetyl or cetearyl alcohol).
- Emulsifier: what lets the water and oil stay mixed. Different emulsifiers need different amounts and methods, so follow the supplier's instructions for the one you bought.
- Preservative: a broad-spectrum preservative, added at the temperature and in the pH range its supplier gives. In the EU and Great Britain, only the preservatives listed in Annex V of the cosmetics regulation may be used, each up to its legal maximum.
- Cool-down phase: heat-sensitive ingredients such as fragrance, some extracts and vitamin E (tocopherol), added once the batch has cooled to the temperature their suppliers give.
A formula that adds up is not the same as a formula that works. The calculator cannot tell whether an emulsion will stay stable, whether a preservative works at your formula's pH, or whether ingredients suit each other. Professional formulators test stability and run a preservative efficacy (challenge) test, such as ISO 11930, before a product is sold.
Sources
- US FDA, Microbiological safety and cosmetics: how cosmetics become contaminated, including an ineffective preservation system.
- Regulation (EC) No 1223/2009 on cosmetic products, EUR-Lex: Annex V lists the preservatives allowed in cosmetics and their maximum concentrations.
- GOV.UK, Making cosmetic products available to consumers in Great Britain: safety assessment by a qualified safety assessor and the Responsible Person.
- ISO 11930:2019, Cosmetics — Microbiology — Evaluation of the antimicrobial protection of a cosmetic product: the preservation efficacy test.
Questions
Why must the percentages add up to exactly 100 %?
A percentage formula describes the whole product. If the numbers add up to 98 %, the weights for your batch come out 2 % short, and topping up afterwards changes every ingredient's share. Tick Balance on the water row and the calculator gives it whatever is left, which is how many published formulas write it (often as “q.s. to 100 %”).
What usage rate should I use for my emulsifier and preservative?
The one your supplier gives for that exact product. Emulsifiers and preservatives sold under similar names can need very different amounts, and preservatives also have legal maximum concentrations (in the EU and Great Britain they are listed in Annex V of the cosmetics regulation). Enter the supplier's minimum and maximum on the ingredient's row and the calculator flags anything outside them.
Does a lotion really need a preservative?
Anything that contains water, including hydrosols and aloe juice, can grow bacteria, yeast and mould, often before you can see or smell anything. It needs a broad-spectrum preservative that covers all three, used at the supplier's rate and within the pH range it works in. Balms and body butters made without any water are a different case, but they still need clean equipment and dry hands.
How do I turn a recipe in grams into percentages?
Divide each ingredient's weight by the total weight of the batch and multiply by 100. The recipe batch scaler does this in one step: paste the recipe in grams and scale it to 100 g, and the new gram figures are the percentages.
Is a formula that adds up safe to use or sell?
Not necessarily. The calculator checks arithmetic, not safety: it cannot tell whether the emulsion will stay stable or whether the preservative works in your formula. In Great Britain and the EU, a cosmetic needs a safety assessment by a qualified safety assessor before it is sold, and a preservative efficacy test is the usual way to show that the preservation works.