Perfumer's Alcohol: Ratios and Batch Math

Updated November 2026

A perfume batch is two numbers and one constraint. The two numbers are how much finished liquid you are making and what share of it is fragrance oil; the remainder is perfumer’s alcohol. The constraint is the IFRA Category 4 maximum for the particular oil you have chosen, which is set per fragrance and is the figure that decides whether the share you picked is one you can actually use. This page carries the arithmetic, worked at the sizes brands actually bottle, and the Category 4 range across our own catalogue.

What Perfumer’s Alcohol Actually Is

Perfumer’s alcohol is ethanol that has been denatured — made undrinkable — so it can be sold for industrial use rather than as a beverage. In the United States the grade usually sold for fragrance is SDA 40-B, specially denatured alcohol denatured with a small quantity of tert-butyl alcohol and a trace of denatonium benzoate, the bittering agent. It is commonly supplied at 200 proof, and a 190-proof grade also exists. Some suppliers sell a blend that already carries a little dipropylene glycol or monopropylene glycol; others sell the ethanol alone and leave that choice to you.

What matters for a formula is that the denaturant load is small enough that it does not interfere with the fragrance, and that the alcohol is the diluent — it carries the oil, flashes off the skin and takes the top notes with it. It is not a fixative and it does not make a fragrance last longer; what it changes is how far and how fast the fragrance travels. Our note on strength, longevity and diffusion covers that difference in detail.

One practical consequence of using a high-proof alcohol: the finished product is flammable, and so is the concentrate you are weighing out. The flashpoint on a fragrance oil’s safety data sheet describes the oil, not the blend, and a blend in ethanol will flash far lower than the oil alone.

The Concentration Bands, and What They Are Not

The words on the label describe a house’s intent, not a measured percentage.

Every guide to perfume making opens with the same ladder: cologne at the bottom, extrait at the top, with toilette and parfum in between. The ladder is useful as a starting point and it is worth being precise about what it is. No regulation we could find in the United States or the European Union assigns a percentage to any of those words. They are trade conventions, they vary between houses, and two bottles labelled differently can sit at the same strength.

Name on the label	Fragrance oil, by convention	Perfumer’s alcohol
Eau de cologne	2–5%	95–98%
Eau de toilette	5–15%	85–95%
Eau de parfum	15–20%	80–85%
Parfum / extrait	20–40%	60–80%

Published ranges differ from source to source; these are the ones most commonly quoted. Treat the band as a design target and the IFRA maximum below as the ceiling.

IFRA takes the opposite approach. It does not care what the label says: alcoholic fine fragrance — cologne, toilette, parfum, extrait — is grouped as Category 4, and the maximum is set per fragrance rather than per category name. The 51st Amendment guide sets out the full category list and how the limits are derived.

How Much Alcohol for Your Batch

The arithmetic is one line. Total volume × the oil percentage is the oil; the remainder is the alcohol. Two worked examples, at the sizes brands actually bottle:

Two things the arithmetic does not tell you. First, allow for loss: liquid stays in the beaker, on the funnel and in the filter, and a run sized to exactly 360 ml will fill eleven bottles and most of a twelfth. Adding 3–5% to the batch is normal practice. Second, the percentages above are of the finished liquid, which is the way usage rates are written on an IFRA sheet; if you are used to thinking of an addition to a base, that is a different number and it will not match.

If you would rather not do the arithmetic each time, our fragrance oil calculator works the same conversion for any batch size and any usage rate.

By Weight or by Volume?

Most professional formulas are written as a percentage by weight, and weighing is the more repeatable of the two methods — a balance does not care about temperature, meniscus or how well the cylinder drains. The two bases are not interchangeable, and the gap is large enough to matter.

Ethanol has a density of about 0.789 g per ml at 20 °C. A fragrance oil is usually nearer 1.00 g per ml, though it varies by composition and the figure for a specific oil is on its safety data sheet. Take the 360 ml batch above: 75.6 ml of oil at 1.00 g per ml is 75.6 g, and 284.4 ml of alcohol at 0.789 is 224.4 g, giving 300.0 g in total. The oil is 25.2% of that batch by weight, not 21%.

Neither basis is wrong. What causes trouble is changing basis halfway, or scaling a batch written one way with a measurement taken the other. Write the basis on the formula sheet, in words, beside the percentage. Our guide to reading an SDS and an IFRA sheet covers which figures on those documents are weight-based.

The Limit That Actually Binds

The band you choose is a design decision. The IFRA Category 4 maximum is not: it is a number set per fragrance, published on that fragrance’s IFRA 51 document, and it is the ceiling for an alcoholic fine fragrance applied to skin.

We read the Category 4 maximum for all 72 of our stock oils on 7 November 2026. Across the catalogue it runs from 4.30% to 40.00%, with a median of 31.45%; 31 of the 72 carry the sheets’ top figure of 40.00%. The spread is the point. A single house number applied across a collection will be comfortable for some oils and over the limit for others.

If your perfume is built at	Oils over their Category 4 maximum
5% fragrance oil	1 of 72
10% fragrance oil	6 of 72
15% fragrance oil	11 of 72
20% fragrance oil	20 of 72
21% fragrance oil	21 of 72
25% fragrance oil	29 of 72

Counted across all 72 stock oils from their IFRA 51 documents, read 7 November 2026.

The oils with the lowest Category 4 ceilings in our range are Ultraviolet at 4.30%, Plant-Based Orchard at 7.37%, Clemenpine at 8.33%, Solair at 8.60%, Plant-Based Herb Garden at 9.18% and Chocoholic at 9.85%. At the other end, Eau de Rose and thirty others carry 40.00%. Every oil’s figure is on its own product page under Documentation, and the whole set is on our perfume and cologne collection.

A maximum is not a recommendation. It is the highest level the safety assessment supports for that category, and most fragrances are at their best well below it. Where your product sits, and how you use these figures, is your own responsibility as the brand placing it on the market.

Maceration and Rest

Blotters at intervals, with a control, are how a rest is judged.

Most formulators rest a finished perfume before bottling, and the published guidance is genuinely inconsistent. Two to four weeks in a cool, dark place is the range quoted most often; some writers recommend four to eight weeks; a minority argue the difference is small enough to be imagined. The honest position is that this is an easy thing to test and a poor thing to assume.

If you want to know what resting does to your own formula, hold back a small control at mixing, keep both samples in the same place, and smell them side by side on blotters at one, two and four weeks. Write down what you find. A fragrance that goes out the door at four weeks because the batch sheet said four weeks, without anyone having compared it to a control, is a schedule rather than a result. Chill-filtering after the rest, if your blend throws any haze, is a separate step and a common one.

Before You Scale: The Alcohol Permit

This one catches brands between the sample bench and the first production run. In the United States, specially denatured alcohol is regulated by the Alcohol and Tobacco Tax and Trade Bureau under 27 CFR Part 20. A business that receives and uses it needs a TTB industrial alcohol user permit, and a supplier may not ship specially denatured spirits to you until it holds a copy of that permit. TTB publishes the requirements for new users and dealers directly.

The practical point is one of sequence. The permit takes time; a purchase order does not. If a production run is scheduled around alcohol you cannot legally receive yet, the run moves. Start the application before the formula is finished.

Common Questions

How much perfumer’s alcohol do I need for twelve 30 ml bottles?

Twelve 30 ml bottles is a 360 ml batch. At 21% fragrance oil by volume that is 75.6 ml of oil and 284.4 ml of perfumer’s alcohol. The arithmetic is total volume × the percentage for the oil, and the remainder for the alcohol — allow a little extra for what stays in the beaker and the filter.

What is the fragrance oil to perfumer’s alcohol ratio for eau de parfum?

By long-standing trade convention eau de parfum sits around 15–20% fragrance oil, eau de toilette around 5–15%, eau de cologne around 2–5% and parfum or extrait around 20–40%. These are conventions, not rules: we could find no US or EU regulation that assigns a percentage to any of those words, and houses label the same strength differently.

Is 21% fragrance oil safe in a perfume?

It depends entirely on the oil. IFRA treats alcoholic fine fragrance as Category 4 and sets a different maximum for every fragrance. Across our own 72 IFRA 51 sheets, read on 7 November 2026, the Category 4 maximum ranges from 4.30% to 40.00% with a median of 31.45% — and 21 of the 72 carry a Category 4 maximum below 21%. Read the sheet for the oil you are using before you scale a batch.

Should I measure by weight or by volume?

Weight is the more repeatable of the two, and most professional specifications are written as a percentage by weight. The two are not interchangeable: ethanol weighs about 0.789 g per ml, so a batch mixed at 21% oil by volume works out near 25% by weight when the oil is close to 1.00 g per ml. Pick one basis, write it on the formula, and stay on it.

How long should perfume rest after mixing?

Published guidance disagrees. Two to four weeks in a cool, dark place is the most commonly recommended rest, some formulators go to eight weeks or longer, and a minority hold that the change is small. Treat the rest as something to test rather than a number to take on faith: keep a control, smell the batch on a blotter at intervals, and write down what you find.

Do I need a permit to buy perfumer’s alcohol in the United States?

Specially denatured alcohol is regulated by the Alcohol and Tobacco Tax and Trade Bureau under 27 CFR Part 20. A business that receives and uses it needs a TTB industrial alcohol user permit, and a supplier may not ship specially denatured spirits until it holds a copy of that permit. Plan the permit before the production run, not after.