Cosmetic Formula Batch Calculator (% to grams)

How it works

Grams of each ingredient = percent ÷ 100 × batch weight; formula must total 100%; emulsifier ≈ 20–25% of the oil phase; preservative at the supplier’s rate (typically 0.5–1.5%) whenever water is present

Cosmetic formulas are written in percentages so that they can be made at any size and compared with other formulas; converting to grams is then a single multiplication per line, which is why formulators work by weight and never by volume — water, oils and butters all have different densities and drops are meaningless. A formula must add to exactly 100, with water usually taking up the slack, and it is organised in phases: the water phase and oil phase are heated separately and combined to form the emulsion, and heat-sensitive ingredients — preservative, fragrance, actives, vitamin E — go in as the “cool-down” phase below about 40 °C. The checks here catch the classic beginner errors: an unpreserved water-containing product, too little emulsifier for the oil load, or a preservative outside its effective range.

Worked example

A 500 g lotion batch from an 8-ingredient formula: 355 g water, 15 g glycerin, 40 g shea, 50 g almond oil, 30 g emulsifying wax, 2.5 g preservative, 2.5 g vitamin E and 5 g fragrance — the formula sums to 100%, the emulsifier is a third of the 18% oil phase, and it fills ten 50 g jars at roughly $2.10 each with packaging.

Frequently asked questions