Short answer
When a formula contains diluted materials, each row has three different percentages. Formula % is the row's weight over the formula's total weight — its physical share. Absolute % is the row's pure material over the total weight — how concentrated that material is in the mixture. Relative % is the row's pure material over the total pure material — its share of the fragrance itself, ignoring solvent. A material weighed as a 10% solution can be 10% of a formula by weight, 1% of it in absolute terms and 1.16% of its scent.
Why one row needs three numbers
Perfumers dilute strong or solid materials before weighing them: a 10% solution of Ambroxan, a 1% solution of a powerful aldehyde, a 10% solution of vanillin in dipropylene glycol. The solution is what goes on the balance, so it is what the formula lists. But the solution is mostly solvent, and solvent does not smell. As soon as a formula holds both neat and diluted rows, "how much of this is in the formula?" has more than one correct answer, depending on whether you mean liquid on the balance, material in the mixture, or material in the scent.
Confusing those answers is not a rounding issue. It changes the amount of a material by a factor of ten or more, which is the difference between a trace and a dominant note — and, for restricted materials, between a compliant formula and one that is not.
The definitions
For each row, first find its pure active weight:
pure active (g) = weighed (g) × dilution ÷ 100
Then:
formula % = weighed ÷ total formula weight × 100
absolute % = pure active ÷ total formula weight × 100
relative % = pure active ÷ total pure active × 100
A neat material (100% dilution) has the same formula % and absolute %. Its relative % is higher whenever the formula contains solvent, because the denominator excludes that solvent.
A worked formula
A 10 g illustrative trial with two diluted rows. Total weight 10.00 g; total pure active 8.65 g; internal solvent from the dilutions 1.35 g.
| Material | Weighed | Dilution | Pure active | Formula % | Absolute % | Relative % |
|---|---|---|---|---|---|---|
| Bergamot oil | 2.00 g | 100% | 2.000 g | 20.00 | 20.00 | 23.12 |
| Lavender oil | 1.50 g | 100% | 1.500 g | 15.00 | 15.00 | 17.34 |
| Hedione | 3.00 g | 100% | 3.000 g | 30.00 | 30.00 | 34.68 |
| Iso E Super | 2.00 g | 100% | 2.000 g | 20.00 | 20.00 | 23.12 |
| Ambroxan | 1.00 g | 10% | 0.100 g | 10.00 | 1.00 | 1.16 |
| Vanillin | 0.50 g | 10% | 0.050 g | 5.00 | 0.50 | 0.58 |
| Total | 10.00 g | 8.650 g | 100.00 | 86.50 | 100.00 |
Formula % totals 100 because it describes the whole mixture. Relative % also totals 100, because it describes the whole fragrance. Absolute % totals 86.50 — the share of the mixture that is fragrance material — and the missing 13.50% is the solvent carried by the dilutions.
Which percentage answers which question
| Question | Use |
|---|---|
| How much do I put on the balance? | Formula % (times the batch size) |
| How much of this material is physically in the mixture? | Absolute % |
| How much of the scent is this material? | Relative % |
| If I re-dilute a material, what must stay the same for the smell not to change? | Its pure active weight, and therefore its relative % |
| How much of this material is in the finished perfume? | Absolute % × concentrate dosage, or relative % × pure-fragrance dosage |
The last row matters for safety. IFRA limits are expressed as the maximum concentration of a material in the finished product. To check one you need grams of pure material per gram of finished product, which you can reach from either absolute or relative %, provided the dosage you multiply by is on the same basis. How to check IFRA limits in a perfume formula works through both routes and shows they agree.
Changing a row's dilution: what stays constant?
Suppose you replace the 10% Ambroxan solution with a 1% solution. There are three reasonable things you might want to hold constant, and each gives a different formula:
- Keep the row's weight. Still 1.00 g on the balance, but now only 0.01 g of Ambroxan. The formula total is unchanged; the material's contribution falls tenfold. Useful when you deliberately want less of it.
- Keep the pure active. To deliver the same 0.10 g of Ambroxan at 1%, you must weigh 10.00 g of solution. The material's contribution to the scent is unchanged, but the formula's total weight rises by 9 g, so every other row's formula % falls.
- Keep the pure active and the total. Weigh 10.00 g of the 1% solution and remove 9 g of a solvent elsewhere in the formula to compensate. This only works if the formula has that much free solvent to give back.
Formulas go wrong when someone changes a dilution without deciding which of these they meant. RUŌOD Lab makes the decision explicit: changing an entry's dilution is done through one of three methods — preserve the row's weight, preserve its pure active, or exchange solvent to keep both pure active and total — and every percentage is recalculated afterwards. You can see how the editor presents them on the calculations section of the product page.
Recording dilutions so the percentages stay recoverable
- Every row records the dilution it was weighed at, even if it is 100%.
- Dilutions are by weight, and the solvent is named (ethanol, DPG, IPM…).
- A dilution is treated as a separate stock item with its own label and date — see how to dilute aroma chemicals.
- Percentages quoted in notes or briefs say which kind they are.
The rest of the core arithmetic — concentration, scaling, conversion — is in the perfume dilution and calculations guide.
Frequently asked questions
Which percentage do published formulas use?
Usually formula % (or parts per thousand) of the materials as listed, with dilutions named in the material column — "Ambroxan 10%". If a published formula does not say whether a material is diluted, you cannot know its true amount, so treat the formula with caution.
Is relative % the same as the "pure oil" percentage?
Yes, if by pure oil you mean the fragrance materials without any solvent. Relative % is each material's share of that.
Should I count a solvent row, like added DPG, as a material?
It is part of the formula's weight, so it counts in formula %. It has no pure active, so it is excluded from relative %.
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.