Short answer
IFRA limits are maximum concentrations of a material in the finished product, by product category. To check a formula, work out how many grams of each restricted material — including restricted constituents that arrive inside natural materials — end up in each gram of finished product, and compare that with the limit for your category. In practice: the material's absolute percentage in the concentrate × the concentrate's dosage in the product. The highest dosage your formula can be used at is set by whichever material reaches its limit first.
What an IFRA limit applies to
A restriction Standard sets the maximum concentration of a material in a finished consumer product, separately for each IFRA product category — fine fragrance, body lotion, rinse-off products, candles and so on. "0.30% in Category 4" means the material may make up at most 0.30% of the finished fine-fragrance product, by weight. It does not mean 0.30% of the concentrate. How the Standards and categories are organized is explained in the IFRA Standards guide.
Three consequences follow:
- The same concentrate can comply at 10% in a perfume and fail at 25%.
- The same concentrate can comply in one category and fail in another with a lower limit.
- Diluted ingredients must be counted by their pure material, not by the weight of solution.
The calculation
level in finished product (%) = absolute % in concentrate × dosage of concentrate (as a fraction)
where absolute % is the material's pure weight divided by the concentrate's total weight, and dosage is the concentrate's share of the finished product. And the reverse, to find the strongest product a formula allows:
maximum dosage (%) = limit (%) ÷ absolute % in concentrate × 100
Calculate it for every restricted material; the formula's maximum dosage is the lowest of them.
A worked example
A 100 g concentrate, to be used at 20% in a fine-fragrance spray. It contains three restricted substances, with illustrative limits:
- Material A, used neat at 1.20 g.
- Material B, used as 5.00 g of a 10% solution — so 0.50 g of B, and 4.50 g of solvent.
- Constituent D, present in two ways: 3.00 g of a natural oil that is 30% D (illustrative), contributing 0.90 g, plus 0.40 g of D added as an isolate. Total 1.30 g.
| Substance | Pure grams in 100 g | Absolute % | In product at 20% | Limit | Result | Max dosage |
|---|---|---|---|---|---|---|
| A | 1.20 | 1.20% | 0.24% | 0.30% | Within | 25.0% |
| B | 0.50 | 0.50% | 0.10% | 0.15% | Within | 30.0% |
| D (from oil + isolate) | 1.30 | 1.30% | 0.26% | 0.20% | Exceeds | 15.4% |
At 20%, the formula fails because of D — and only because D also comes from the natural oil. Counting the isolate alone (0.40% × 0.20 = 0.08%) would have looked comfortably compliant. The formula can be used at up to about 15.4%; at 15% it is within every limit here. Alternatively, reduce the oil or the isolate and recheck.
Two errors are worth seeing in the numbers. If B's dilution were forgotten, its level would appear to be 5.00% × 0.20 = 1.00% — a false failure, ten times too high. And if the concentrate's dosage were applied to the formula % of a diluted row rather than its absolute %, the same error appears. Formula %, absolute % and relative % explains the difference.
Restricted constituents of natural materials
Many natural materials contain restricted substances: citrus oils and furocoumarins, oils rich in citral or eugenol, and others. IFRA publishes an annex listing typical levels of restricted constituents in natural materials ("contributions from other sources"), and suppliers' documents often state them. The limit applies to the total of the substance from every source in the formula, as constituent D showed. Record known constituent levels on the material record so that the calculation can include them; SDS, specifications and CoAs covers where to find them.
The same check from relative percentage
If you work in relative % — each material's share of the fragrance materials, excluding solvent — use a dosage on the same basis. In the example, the concentrate is 95.5 g of fragrance material and 4.5 g of solvent, so at 20% concentrate the product contains 20% × 0.955 = 19.1% fragrance material. D's relative % is 1.30 ÷ 95.5 = 1.361%, and 1.361% × 0.191 = 0.26% — the same answer. Both routes agree as long as the percentage and the dosage share the same basis; mixing bases is where errors come from.
This matters if your software compares limits with relative percentages. RUŌOD Lab, for example, flags a formula row whose relative % exceeds the IFRA limit recorded on that material. To use that check precisely, record the limit on the same basis: the finished-product limit divided by the fragrance-material dosage you intend. For D at 19.1%, that is 0.20 ÷ 0.191 = 1.047%. If you record the finished-product limit itself (0.20%), the check is stricter than necessary — it will flag rows that may be within the limit at your dosage, but it will not let one through. Either way, the app checks only the limits you record, and does not total constituents of natural materials for you, so that part of the check remains yours.
Products in more than one category
If a product falls into two categories — a body mist used on skin and hair, for example — the conservative approach, and the one IFRA's guidance describes, is to apply, for each material, the lower of the limits that apply. When in doubt about a product's category, IFRA's guidance document has the category definitions; your safety assessor will decide for products you sell.
What this calculation does not do
- It does not make a product safe or legal. IFRA conformity is one input to a product safety assessment, which many markets require separately.
- It does not cover prohibited materials, which are not allowed at any level beyond trace impurities, or specifications such as purity requirements.
- It does not replace market rules such as the EU's allergen labelling, which uses its own thresholds (see EU fragrance allergen labelling).
Fragrance oils bought from a supplier are usually accompanied by an IFRA certificate that has done this calculation for the oil as a whole; IFRA certificates of conformity explains how to read one. To convert concentrate dosage to grams for a batch, see how to calculate perfume concentration.
Sources
- IFRA — IFRA Standards
- IFRA — Using the Standards (including the most-restrictive-ingredient principle)
Frequently asked questions
Is the IFRA limit a percentage of the perfume oil or of the finished perfume?
Of the finished product. For a fragrance oil sold to you, the supplier's certificate usually states the maximum percentage of that oil in the finished product for each category, which already accounts for its restricted components.
Do I need to count materials I used in tiny amounts?
Yes, if they are restricted. Powerful restricted materials are often used in tiny amounts, and so are their limits.
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.