Bench math · Field note no. 02 May 2026
How to calculate dilution for an Eau de Parfum
A working perfumer's reference for dilution math: concentrate-to-alcohol ratios, gram weights, and the small adjustments that separate a good batch from a great one.
Dilution is the most boring step in perfumery and the one most often done wrong. The maths is trivial; the discipline is in writing it down so the next batch is identical to this one. This guide is a working reference for building an Eau de Parfum, with the same numbers you would use for an EDT or an extrait.
The four standard concentrations
The trade names refer to the percentage of fragrance concentrate dissolved in perfumer's alcohol. There is no formal standard, different houses pitch their EDT a few points higher or lower, but these ranges are what most labs and label printers expect:
| Form | Concentrate | Typical use |
|---|---|---|
| Cologne / Eau Fraîche | 3–5 % | Splash, summer scents, citrus. |
| Eau de Toilette | 8–12 % | Daytime sprays, designer briefs. |
| Eau de Parfum | 15–22 % | The everyday workhorse. |
| Extrait / Parfum | 22–35 % | Roll-ons, decants, long projection. |
For an EDP, 20 % is a sensible default. It gives you headroom on projection without pushing the ethanol burn. If your formula leans heavy on top notes, drop to 18 %. If it's mostly base materials and you want presence, push to 22 %.
The formula you actually need
Two equations cover almost every dilution decision you will make at the bench:
Concentrate by weight
concentrate_g = batch_g × (concentration_pct / 100)
alcohol_g = batch_g − concentrate_g
Notice the units: grams, not millilitres. Perfumer's alcohol is roughly 0.79 g/mL and concentrates vary from 0.85 to 1.05 g/mL depending on material mix. Working in grams avoids density bookkeeping and matches what your lab balance reads directly.
Worked example: a 30 mL EDP at 20 %
A 30 mL bottle of Eau de Parfum, dosed at 20 % in 96 % perfumer's alcohol. Approximate the batch as 30 g, close enough at this concentration that the small density correction does not matter for a hand-mixed batch:
| Component | Grams | Notes |
|---|---|---|
| Concentrate (the formula) | 6.000 g | 30 × 0.20 |
| Perfumer's alcohol (96 %) | 24.000 g | 30 − 6 |
| Total | 30.000 g | ≈ 30 mL finished |
Each material in the concentrate scales the same way. A jasmine absolute
listed at 4.5 % of the concentrate appears in the bottle as
6.000 × 0.045 = 0.270 g. Build a column for grams in your
formula sheet and the rest is one row at a time.
Pre-dilutions and dilution lines
Some materials are too potent to weigh accurately at neat strength , aldehyde C-14, iso E super at trace levels, anything dosed below 0.5 % of the concentrate. Standard practice is to keep 10 % dilutions in DPG (dipropylene glycol) or in a small portion of the alcohol you'll later add to the batch.
When a material is added as a 10 % dilution, multiply its grams by 10 to get the working amount of the dilution. A material specified at 0.30 g neat becomes 3.00 g of the 10 % stock. Mark it clearly on the bench sheet, confusing neat and dilution by a factor of 10 is the most common bench error after misreading a balance.
Maturation and rest periods
Once the concentrate is dissolved in alcohol, the EDP is not finished. The bench convention is:
- 24 hours room temperature for the alcohol burn to integrate.
- 2–4 weeks at 18 °C, dark glass, sealed for the molecules to settle and the top notes to soften.
- Optional cold filter at 4 °C for 48 hours, then through 0.45 µm paper, for clarity.
Resin-heavy or absolute-heavy formulas benefit from longer maceration , six to eight weeks is not excessive for a chypre or an oriental.
Common errors and how to catch them
Working in millilitres for the concentrate
A graduated cylinder is fine for alcohol. Concentrate goes on the balance. The density variance between materials is large enough that volumetric measurement of the concentrate introduces 5–10 % error per batch, which is the difference between a Studio sample and a sellable bottle.
Skipping the tare
Tare the balance with the empty vessel before every component. A formula sheet that reads "0.270 g jasmine" should be the delta on the balance, not the cumulative reading.
Forgetting the alcohol density
For finished-volume targets (e.g. "I need exactly 30 mL"), use
alcohol_mL = alcohol_g ÷ 0.79. Add the alcohol last,
volumetrically, to land on the bottle size.
The takeaway
Dilution is just two equations and a balance. The work is in the bench discipline, gram weights, dated batches, lot numbers, and a sealed log of every change. Get that right and the second batch will smell like the first one. Get it wrong and you're back to chasing a phantom drift in your top notes that turns out to be a 4 % miscount in your alcohol.