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Soap Math

How to Use IFRA Math

Fragrance Safety & Compliance Calculator

IFRA Math helps you check whether your fragrance blend is safe to use in a specific product type. It calculates the maximum usage rate for your blend based on IFRA (International Fragrance Association) standards, identifies restricted and fully-prohibited components in your essential oils, and flags EU allergens that may require label declaration. Whether you're making soap, lotion, perfume, or candles, IFRA Math ensures your fragrance levels stay within safe limits — and warns you when an oil contains a material banned from all product categories entirely.

What Is IFRA?

The International Fragrance Association (IFRA) is the global representative body of the fragrance industry. IFRA publishes safety standards that set maximum usage levels for fragrance ingredients based on scientific research and safety data. These standards are organized by product category — different product types have different limits because of how they contact the skin.

The current edition is the IFRA 51st Amendment (January 2023), which covers 263 materials in two groups: 171 with per-category usage limits, and approximately 90 that are fully prohibited from all product types at any concentration. The IFRA 51st Amendment Reference Table lists all 263 entries with their limits.

How to Use IFRA Math

Follow these steps to check your fragrance blend against IFRA safety limits.

1

Select Oils

Search for an essential oil or fragrance material in the oil library and add it to your blend.
2

Set Ratios

Set the percentage of each oil in your fragrance blend (all oils should total 100%).
3

Review Components

Review and adjust the chemical components listed for each oil. You can edit concentrations or add missing components from your supplier's SDS.
4

Process Compliance

Click "Calculate Compliance" to generate your IFRA results report.
5

Review Results

Review the results — the report shows maximum usage rates for all 18 IFRA categories, component breakdowns, and EU allergen declarations. Categories where your blend is prohibited show PROHIBITED in red. Click the underlined text to see which specific component triggered the result and which oil it came from. A summary also appears below the table for printing.

Example Check

You're blending lavender (70%) and tea tree (30%) for a body lotion. Add both oils, set their percentages, and calculate. The report will show that for Category 5A (body creams), your maximum fragrance usage rate might be 4.2%, meaning your finished lotion should contain no more than 4.2% of this blend.

Two Types of PROHIBITED Results

When the results show PROHIBITED, the cause and your options depend on which type it is:

Category-Level Prohibition

The blend contains a component whose limit is 0% in that specific category but may be allowed in others. For example, a blend containing bergamot expressed oil may be PROHIBITED in leave-on body products (Category 5A) due to furocoumarins, but still allowed in rinse-off soap (Category 9) or candles (Category 12). You can still use this blend — just not in the prohibited product types.

Globally Prohibited (All 18 Categories)

When every single category shows PROHIBITED, your blend contains a material banned from all product types under the IFRA 51st Amendment — at any concentration. Examples include Safrole (in cinnamon bark, sassafras, camphor), Benzyl cyanide (in jasmine absolute, ylang ylang, neroli), and 7-Methoxycoumarin (in lavender absolute, lemon expressed). There is no dilution that makes these compliant. You must remove the offending oil from the blend or substitute it with a processed version free of the prohibited component.

In results, click the underlined PROHIBITED text in any cell to see the specific component and which essential oil it comes from.

IFRA Categories

IFRA groups products into 18 categories based on exposure type and skin contact area. Here are the main categories:

Category 1 — Lip Products & Toys

Products applied to or near the lips and children's toys. Strictest limits due to potential ingestion.

Category 2 — Deodorants & Body Sprays

Products applied to underarms and body. Relatively strict limits due to prolonged skin contact on sensitive areas.

Category 3 — Eye & Facial Makeup

Eye products, makeup, and facial treatment masks. Strict limits due to contact with delicate facial skin.

Category 4 — Perfume & Fine Fragrance

Perfume, cologne, solid perfume, and fragranced bracelets. Applied directly to skin in concentrated form.

Categories 5A–5D — Leave-On Body, Face, Hand & Baby

Body creams (5A), face creams and beard oils (5B), hand creams (5C), and baby products (5D). Limits vary by body area and user sensitivity.

Category 6 — Oral Care

Mouthwash, toothpaste, and breath sprays. Very strict limits due to oral exposure.

Categories 7A–7B — Hair Products

Rinse-off hair treatments (7A) and leave-on hair treatments (7B). Leave-on products have stricter limits.

Category 8 — Wipes

Intimate wipes and baby wipes. Moderate limits for brief skin contact products.

Category 9 — Rinse-Off Products

Bar soap, liquid soap, shampoo, and shower gel. More relaxed limits because the product washes off quickly.

Categories 10A–10B — Household & Air Care

Cleaning products and reed diffusers (10A), air freshener sprays (10B). Different exposure profiles than skin contact products.

Categories 11–12 — Non-Skin Contact

Diapers and scented clothing (11A–11B), candles, incense, and air fresheners (12). Generally more relaxed limits.

Safety & Logic

IFRA limits are based on the actual risk posed in each product type — and risk depends on how long a product stays on the skin, where it's applied, and who uses it. An ingredient that is dangerous in a leave-on cream applied all over the body every day may be perfectly safe in a rinse-off shampoo that washes off within seconds.

Phototoxic oils (bergamot expressed, cold-pressed citrus peel oils) — prohibited in leave-on skin products; allowed in rinse-off and non-skin-contact products. The furocoumarin-free (FCF) versions of these oils are typically unrestricted.
Strong sensitizers (e.g. certain components in cinnamon bark, clove bud, Peru balsam) — may be prohibited from multiple categories or have near-zero limits everywhere. Sensitization risk is dose and frequency dependent.
Oral-category prohibitions — some materials are banned from Category 6 (mouthwash, toothpaste) that are otherwise fine in skin products due to oral mucosa absorption and ingestion risk.
Baby product prohibitions (Category 5D) — materials that are acceptable on adult skin may be banned from baby products due to underdeveloped skin barrier and metabolism.

How the IFRA Calculator Works

IFRA Math uses the IFRA 51st Amendment dataset to perform multi-stage compliance checks:

  • Component-Level Analysis: The calculator looks inside each essential oil to find regulated chemical components (like Citral, Linalool, or Cinnamaldehyde).
  • Aggregate Concentration: If multiple oils in your blend contain the same regulated component, the calculator adds them together to find the total concentration in the blend.
  • Category-Specific Limits: The total concentration of each component is checked against the IFRA limit for each of the 18 product categories.
  • Limiting Factor Identification: The calculator identifies which specific component reaches its limit first — this is what determines the "Maximum Usage Rate" for your entire fragrance blend.

Frequently Asked Questions

Ready to check your fragrance safety?

Use IFRA Math to calculate safe usage levels for your essential oil blends and ensure compliance.

Open IFRA Math →

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