Short answer
To compare two perfume formulas properly, put them on the same basis first: convert both to percentages of pure material (so dilutions and solvents do not distort the picture), break any premixes into their constituents, and match materials by identity rather than by name. Then list every material with its share in each formula and the difference in percentage points, sort by the size of the difference, and flag materials that appear in only one formula. Comparing raw weights or rows as written is the usual mistake: two formulas can look very different on paper and smell almost the same, or the reverse.
When you need a comparison
- Two versions of your own formula — what exactly changed?
- A formula you have inherited against your current one.
- Your formula against a manufacturer's working copy, before production.
- A reformulation against the original, before a sensory test.
Version control records what you changed and why (see perfume formula version control). A comparison is the check that the records and the formulas agree — and the only tool when there is no change record.
Step 1: the same basis
Decide what you are comparing. For "do they smell alike?", compare relative %: each material's share of the pure fragrance material, ignoring solvent. For "are they physically the same mixture?", compare formula % as written. The difference matters whenever dilutions or solvent rows differ; the three percentages are explained in formula %, absolute % and relative %.
If one formula is in grams, one in parts and one in percent, convert all to percent first. If they weigh a material at different dilutions, convert to pure material.
Step 2: break down premixes
If one formula uses an accord as a single row and the other uses its constituents, they cannot be compared until both are exploded to the same level. The arithmetic is in how to calculate a premix inside a formula.
Step 3: match materials by identity
"MDJ", "Hedione" and "methyl dihydrojasmonate" are one material; "lavender oil" from two origins may not be. Match on a code or CAS number plus grade, and note where two rows that look alike are actually different grades or suppliers.
Step 4: the difference table
An illustrative comparison of two versions, both on a relative-% basis:
| Material | v3 | v4 | Difference (points) | Relative change |
|---|---|---|---|---|
| Iso E Super | 30.0% | 26.0% | −4.0 | −13% |
| Bergamot oil | 18.0% | 21.0% | +3.0 | +17% |
| Hedione | 25.0% | 25.0% | 0 | 0% |
| Ambroxide | 0.8% | 1.2% | +0.4 | +50% |
| Pink pepper oil | — | 0.8% | +0.8 | New |
| Musk and others | 26.2% | 26.0% | −0.2 | −1% |
| Total | 100.0% | 100.0% |
Both columns matter. The difference in points shows where the bulk of the formula moved (Iso E Super, bergamot). The relative change shows where a small material changed a lot — ambroxide is up by half, which may matter more to the smell than the four-point shift in Iso E Super. Strength is not proportion; see odor thresholds in perfumery.
Step 5: read it like a perfumer
- Sort by absolute difference to see the structural changes.
- Then scan the relative changes of powerful materials.
- List additions and removals separately; they are easy to overlook in a long table.
- Check the totals and the solvent: a change in solvent changes the concentrate's strength even if the fragrance is identical.
- Check restricted materials in the new version — any increase needs a fresh compliance check; see how to calculate IFRA compliance.
Doing it in a spreadsheet
Put both formulas in one long table (formula, version, material code, relative %), then build a pivot or lookup table with materials as rows and versions as columns. Add the difference columns, and conditional formatting for additions and removals. A long-table structure also makes it easy to find every formula that uses a material; see the perfume formula spreadsheet. The template that records formulas in that shape is in the perfume formula template.
In RUŌOD Lab, each formula shows its rows with formula %, absolute % and relative % calculated by the same engine, so two versions can be read side by side on the same basis; a duplicate of a formula makes a marked copy you can change without touching the original. The difference table itself is something you build from the two versions, by hand or by exporting both to CSV or Excel.
Frequently asked questions
How big a difference will I smell?
The table cannot tell you. Use it to decide what to test, then test — a triangle test is designed for exactly that question.
Should rounding differences count?
Ignore differences smaller than your formulas' rounding, but check that they are rounding and not a real change hidden in the noise.
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.