How to dilute perfume oil: concentrations for parfum, EDP, EDT and cologne

To turn a perfume concentrate (your blended oils) into a finished perfume, weigh the concentrate, then add perfumer's alcohol until the concentrate makes up the percentage you want: roughly 20–30% for a parfum, 15–20% for an eau de parfum, 5–15% for an eau de toilette and 2–5% for a cologne. Always work by weight, not by drops or millilitres, and let the perfume rest before you judge it.

The rest of this guide shows the maths, the materials and the mistakes that cost people the most.

The usual concentration ranges

There is no legal definition of these names. Each house sets its own levels, so treat these as the ranges most perfumers work within:

Stronger is not always better. Some compositions smell flat or heavy at 25% and open up at 15%. Make two or three small dilutions of the same concentrate and compare them on blotters over a day.

Why you weigh, not count drops

Drops change size with the material, the dropper and the temperature. A drop of a thin citrus oil and a drop of a thick resin are not the same amount. Every serious formula is written as weights or percentages by weight, and a digital scale reading to 0.01 g costs less than a few bottles of wasted material.

Volume causes a second problem: perfumer's alcohol is lighter than water. Ethanol weighs about 0.79 g per millilitre, so a 50 ml bottle holds roughly 40 g of an alcohol-based perfume, not 50 g. If you plan by weight and fill by volume, you will run short.

The maths, with a worked example

You want 50 g of eau de parfum at 18%.

1. Concentrate needed: 50 g × 18% = 9 g.
2. Alcohol needed: 50 g − 9 g = 41 g.
3. Weigh the 9 g of concentrate into a clean glass bottle, then add the alcohol on the scale until the total reads 50 g.

The same formula works for any size: concentrate = batch weight × concentration, and the alcohol is the rest.

To fill a number of bottles, work backwards from volume. Ten 30 ml bottles need about 300 ml, which is roughly 240 g of finished perfume (using about 0.8 g per ml). Add 5–10% for losses in funnels and filters.

Scaling the concentrate itself

If your formula is written in parts or percentages, scale it to the weight of concentrate you need. A formula that adds up to 100 parts, needed as 9 g, means each part is 0.09 g. A material at 12 parts becomes 1.08 g.

This is where very small amounts appear. A material at 0.2 parts in a 9 g batch is 0.018 g, which most scales can't weigh accurately. The usual fix is to keep that material pre-diluted (for example at 10% in alcohol or another solvent) and weigh ten times as much of the dilution. Remember that the solvent in your dilutions counts toward the alcohol.

What to dilute with

• Perfumer's alcohol is high-strength ethanol, denatured so it isn't taxed as a drink. Buy it from a perfumery supplier. Don't use rubbing alcohol: isopropanol smells harsh and is not used in fine fragrance.
• A little water (distilled, 0–5% of the finished perfume) is sometimes added to colognes and EDTs to soften the alcohol. Add it slowly: some materials turn cloudy.
• For perfume oils, use a light, stable carrier such as fractionated coconut oil or jojoba. Oils don't evaporate, so the scent projects less but sits on the skin for longer.

Rest, chill and filter

Freshly mixed perfume often smells sharp and disjointed. Let it rest (perfumers call it maceration) in a closed bottle, in the dark, at room temperature for at least a few days, and usually two to six weeks. Smell it once a week and note the changes.

If the perfume is hazy, chill it in the fridge for a day or two, then filter it through a coffee filter or lab filter paper while it's cold. This removes waxes from naturals and keeps the finished bottle clear.

Two checks before you call it finished

Safety limits apply to the finished perfume. The IFRA Standards limit many materials as a percentage of the finished product, so the same concentrate can pass as an EDT and fail as a parfum. Check your limits at the concentration you will actually sell.

Allergens are counted in the finished perfume too. In the EU, fragrance allergens above 0.001% of a perfume must be named on the label. At EDP strength that is almost every allergen in your concentrate. See the EU allergen labelling rules.

Work safely: never put undiluted materials on your skin, keep alcohol away from flames, and label every bottle with what it is and the date.

Doing it in Nezzo

In Nezzo you write the formula once, set the concentration and the batch weight, and it works out the grams of each material, including the ones you keep pre-diluted. Change 18% to 15% or 50 g to 240 g and every weight updates, so the maths above happens for you.