Short answer
To convert a perfume formula from percentages to grams, multiply each percentage by the batch size and divide by 100: 12.5% of a 40 g batch is 5.00 g. To go the other way, divide each weight by the formula's total weight and multiply by 100. Round only at the end, to a precision your balance can weigh, and check that the rounded grams still add up to the batch size.
Percentages to grams
grams = percentage ÷ 100 × batch size (g)
Take a simple illustrative formula written in percentages and make a 40 g batch of it:
| Material | Percentage | Calculation | Grams |
|---|---|---|---|
| Hedione | 35.0% | 0.350 × 40 | 14.00 |
| Iso E Super | 25.0% | 0.250 × 40 | 10.00 |
| Bergamot oil | 20.0% | 0.200 × 40 | 8.00 |
| Lavender oil | 12.5% | 0.125 × 40 | 5.00 |
| Ambroxan 10% solution | 5.0% | 0.050 × 40 | 2.00 |
| Vanillin 10% solution | 2.5% | 0.025 × 40 | 1.00 |
| Total | 100.0% | 40.00 |
Notice that the diluted materials stay diluted. The formula says 5% of Ambroxan 10% solution, so you weigh 2.00 g of the solution — not 2.00 g of Ambroxan, and not 0.20 g. The dilution is part of the ingredient's identity in the formula, and it must travel with it. How to dilute aroma chemicals explains how those solutions are made and recorded.
Grams to percentages
A weighed trial is easiest to compare with other trials once it is expressed as percentages:
percentage = grams ÷ total grams × 100
Suppose a trial was weighed as 3.20 g, 1.90 g, 1.10 g and 0.30 g. The total is 6.50 g, and the first row is 3.20 ÷ 6.50 × 100 = 49.23%. The others are 29.23%, 16.92% and 4.62%, which add to 100.00%.
Always divide by the total of the formula. If the trial included solvent-only rows (for example, extra DPG added as a diluent), they are part of that total, and the percentages describe the physical mixture. If you want each material's share of the scent alone, you need a different denominator — see formula %, absolute % and relative %.
Rounding without losing the total
Round at the last step, to the resolution of your balance. A 0.01 g balance cannot weigh 0.125 g, so a row like that is weighed as 0.13 g (or the batch is made larger). Rounding each row independently can make the total drift by a few hundredths. Two habits stop that becoming a problem:
- Check the rounded total. If it is 40.01 g instead of 40.00 g, that is fine for a trial and worth knowing for a production record.
- Make small rows bigger, not less precise. If a material calculates to 0.03 g, a 0.01 g balance gives you a weighing error of up to a sixth of the amount. Either make a larger batch or use a more dilute solution of that material so the weighed amount is larger.
How to weigh perfume ingredients accurately covers balance resolution and minimum weights in detail.
Parts per thousand
Many professional formulas are written in parts per thousand rather than percentages, so that small materials are whole numbers (8 parts rather than 0.8%). Converting is a matter of moving the decimal point: parts per thousand ÷ 10 = percentage, and grams = parts ÷ 1000 × batch size. Parts per thousand in perfume formulas covers it, including how to keep a 1000-part formula exact.
Changing the batch size
Converting percentages to a different batch size is the same calculation with a new number. If you already have a weighed formula and want more of it, multiply every row by one scale factor instead — how to scale a perfume formula works through that, including scaling around one ingredient you have a fixed amount of.
In a spreadsheet or in software
In a spreadsheet the conversion is one column: =B2/100*$F$1, where B is the percentage and F1 holds the batch size. The risks are the usual spreadsheet ones — a row added below the range of the total, or a pasted value where a formula used to be — which are covered in how to build a perfume formula spreadsheet. In RUŌOD Lab, a formula is stored as weights with dilutions, the percentages are derived from them, and scaling to a new total weight rewrites every row by one factor, leaving dilutions unchanged.
For the other core calculations — concentration, scaling, batch targets — see the perfume dilution and calculations guide.
Frequently asked questions
Can I treat percentages as grams for a 100 g batch?
Yes. At 100 g, each percentage is the number of grams, which is why 100 g is a convenient trial size if you have enough material. For other sizes, multiply.
My percentages add to 99.9%. Does it matter?
For a trial, a rounding difference of 0.1% rarely matters, but find out where it came from. If it is rounding, note it. If a row is missing, it matters a great deal.
Written and reviewed by the RUŌOD Lab team. This article is general education about perfume formulation and record-keeping; it is not legal, regulatory or safety advice, and the examples are illustrations, not validated commercial formulas. How we write and check these guides.