acalculator

How do I weigh a cosmetic formula?

List your ingredients with their percent of the batch, type the batch size, and the cosmetic formula calculator gives the grams to weigh out. It can top the formula up with water to 100% and puts the ingredients in label order.

Your numbers

Units
Ingredients
Row 1
Row 2
Row 3
Row 4
Row 5
Leave water out of the list when it tops up the formula.
Batch
6 ingredients, 250 g in all

Weigh out: Water: 188.8 g (75.5%); Sweet almond oil: 37.5 g (15%); Emulsifying wax: 12.5 g (5%); Glycerin: 7.5 g (3%); Preservative: 2.5 g (1%); Fragrance: 1.25 g (0.5%).

Weigh out
Water: 188.8 g (75.5%); Sweet almond oil: 37.5 g (15%); Emulsifying wax: 12.5 g (5%); Glycerin: 7.5 g (3%); Preservative: 2.5 g (1%); Fragrance: 1.25 g (0.5%)
Water (g)
188.75
Water (%)
75.5
Listed ingredients (%)
24.5
Batch (g)
250

Batch: 6 ingredients, 250 g in all. Weigh out: Water: 188.8 g (75.5%); Sweet almond oil: 37.5 g (15%); Emulsifying wax: 12.5 g (5%); Glycerin: 7.5 g (3%); Preservative: 2.5 g (1%); Fragrance: 1.25 g (0.5%).

What do I weigh out?

How to calculate

Turns a cosmetic or skincare formula in percent (w/w) into grams for any batch size, tops it up with water to 100% if you like, and lists the ingredients in label order.

Example with the default inputs (Batch size 250 g, Top up with water to 100% Yes, Ingredients [Ingredient Sweet almond oil, Percent (w/w) 15%; Ingredient Emulsifying wax, Percent (w/w) 5%; Ingredient Glycerin, Percent (w/w) 3%; Ingredient Preservative, Percent (w/w) 1%; Ingredient Fragrance, Percent (w/w) 0.5%]): Weigh out: Water: 188.8 g (75.5%); Sweet almond oil: 37.5 g (15%); Emulsifying wax: 12.5 g (5%); Glycerin: 7.5 g (3%); Preservative: 2.5 g (1%); Fragrance: 1.25 g (0.5%).

Method: weight of an ingredient = batch weight × its percent ÷ 100. With top-up water: water % = 100 − the sum of the listed percents.

  • Percents are by weight (w/w) of the finished batch, the usual way cosmetic formulas are written.
  • Label order is descending weight, then ingredients at 1% or less in the order typed (21 CFR 701.3(f)).

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Batch size 250 g, Top up with water to 100% yes, Ingredients Sweet almond oil 15; Emulsifying wax 5; Glycerin 3; Preservative 1; Fragrance 0.5 gives Batch 6 ingredients, 250 g in all, Water (g) 188.75, Water (%) 75.5, Weigh out Water: 188.8 g (75.5%); Sweet almond oil: 37.5 g (15%); Emulsifying wax: 12.5 g (5%); Glycerin: 7.5 g (3%); Preservative: 2.5 g (1%); Fragrance: 1.25 g (0.5%).Source: FDA, Cosmetics Labeling Guide (ingredients in descending order of predominance; those at 1% or less in any order after them, 21 CFR 701.3(f)), https://www.fda.gov/cosmetics/cosmetics-labeling-regulations/cosmetics-labeling-guide
  2. Batch size 100 g, Top up with water to 100% no, Ingredients Shea butter 40; Coconut oil 60 gives Listed ingredients (%) 100, Water (g) 0, Weigh out Coconut oil: 60 g (60%); Shea butter: 40 g (40%).Source: FDA, Cosmetics Labeling Guide (ingredients in descending order of predominance; those at 1% or less in any order after them, 21 CFR 701.3(f)), https://www.fda.gov/cosmetics/cosmetics-labeling-regulations/cosmetics-labeling-guide

How it works

Every percent is by weight of the finished batch (w/w). For each ingredient,

grams = batch weight in grams × percent ÷ 100.

Water top-up (on by default). Water % = 100 − the sum of the listed percents, and water grams = batch × water % ÷ 100. It is added as an ingredient named Water when it is more than 0.

Label order. Ingredients above 1% come first, heaviest first (equal percents keep the order typed). Ingredients at 1% or less follow, in the order typed. An ingredient with no name is called Ingredient 1, Ingredient 2, and so on by its row.

Batch sizes convert exactly: 1 kg = 1,000 g; 1 oz = 28.349523125 g; 1 lb = 453.59237 g.

Exact arithmetic. Each value is read as the exact decimal you typed, in its unit, so each weight is an exact fraction until it is rounded for display.

Output format. The headline gives the number of ingredients and the batch in grams (6 ingredients, 250 g in all, 4 significant figures). The answer and the steps list Name: … g (…%) for each ingredient in label order, joined by ; , with grams to 4 significant figures and percents to 6, rounded half up from the exact value. The rows show the water in grams and percent, the sum of the listed percents, and the batch in grams, to 6 significant figures.

When there is no answer.

  • The listed percents add up to more than 100%.
  • The water top-up is off and the listed percents do not add up to exactly 100%.

Assumptions

  • Percents are w/w of the finished batch; nothing evaporates while you mix.

Worked examples by hand

250 g lotion with water. Listed: 15 + 5 + 3 + 1 + 0.5 = 24.5%. Water = 75.5% = 250 × 0.755 = 188.75 g (shown 188.8 g). Oil 250 × 0.15 = 37.5 g; wax 12.5 g; glycerin 7.5 g; preservative 2.5 g; fragrance 1.25 g. Label order: water, oil, wax, glycerin, then preservative and fragrance (1% or less).

100 g body butter, no water. 60% + 40% = 100%. Coconut oil 60 g, shea butter 40 g, heaviest first.

Other questions people ask

How do I convert a cosmetic formula from percent to grams?

Multiply the batch weight by each percent and divide by 100. For a 250 g lotion, 15% oil is 250 × 15 ÷ 100 = 37.5 g, and 0.5% fragrance is 1.25 g.

What does “q.s.” or top up with water mean?

Quantum satis: add as much water as the other ingredients leave to reach 100%. If the listed ingredients add to 24.5%, water is 75.5% of the batch.

Why use percent by weight?

Weights add up exactly and do not depend on how dense each ingredient is. A formula in percent w/w scales to any batch size with the same result.

Why does my formula not add up to 100%?

Either turn on the water top-up, or adjust the percents. The page shows no answer when the listed percents go over 100%, or are under 100% with no top-up.

In what order do ingredients go on a cosmetic label in the US?

In descending order of weight. Ingredients at 1% or less may follow in any order after the others (21 CFR 701.3). The page lists heavier ingredients first, then those at 1% or less in the order you typed.

Should I weigh small amounts like preservatives more precisely?

Yes. A 1% preservative in a 100 g batch is only 1 g, so use a scale that reads to 0.01 g, and follow the supplier’s use rate for each ingredient.