Converting a Hair Color Formula Between Brands
To convert a hair color formula to another brand, read the level and tone digits, match the same level-and-tone family in the new line, then strand-test the result as a starting point. There is no guaranteed exact cross-brand equivalent, because pigment load, base tone, and numbering systems differ between manufacturers. A conversion chart gives you a defensible candidate to test, not a finished formula.
That is the part most "just use this conversion chart" articles leave out. The charts are not wrong to exist, but they are sold as a one-to-one swap, and color does not work that way. If you are switching product lines, covering for a coworker, or rebuilding a client's old formula from a brand you do not carry, the useful skill is not finding the magic equivalent. It is finding a smart starting point and proving it on a strand before it touches the whole head.
Why an exact cross-brand match does not exist
Permanent hair color is a chemical reaction, not a paint chip. The developer's hydrogen peroxide lifts the natural melanin in the hair while the oxidative dye precursors in the tube develop into colored pigment inside the strand. The published review of hair dye chemistry describes exactly this: oxidizers lighten melanin, the natural pigment responsible for hair color, while precursors such as PPD and PTD react with couplers to build the final shade (Comprehensive Review of Hair Dyes, ACS Omega via PMC). The same source notes that precursor concentration alone shifts the result, ranging from roughly 0.05% for lighter colors to 1.5% for darker ones.
That single detail is why two tubes labeled the same level can finish differently. Three things vary from brand to brand, and none of them are printed on the box:
- Pigment load. How much dye is packed into the base. A "natural" 6N in one line can be more or less saturated than a 6N in another, which changes coverage and depth.
- Base tone and underlying warmth. Lines control unwanted warmth differently, so the same level can pull more gold or more ash even before you add a reflect.
- The numbering system itself. The level digit is broadly shared, but the tone digits are proprietary. A "3" means gold in one system and something else in another.
So when a chart tells you brand A's 7.3 "equals" brand B's 7/3, what it really means is "these two are the closest candidates in the same family." Treat that as a hypothesis, not a guarantee.
What does travel: the universal 1-10 level scale
There is one thing you can lean on across professional lines: the level. The International Colour Chart and the level systems used across professional color all rest on the same 1-to-10 (sometimes 1-to-12) depth scale, where 1 is black and 10 is the lightest blonde. Level measures depth, how light or dark the hair is, independent of tone. It is the most portable piece of information you have, because a level 7 is a level 7 whether the tube comes from Wella or L'Oreal Professionnel.
Professional shade numbers are written as level first, then tone, separated by a dot or a slash. Wella's Koleston and Illumina lines and L'Oreal Professionnel's Majirel both use this level.tone (or level/tone) convention, where the leading number is the depth and the following digits are the primary and secondary reflect. Read left to right:
| Notation | Reads as | What it tells you |
|---|---|---|
| 7.3 | Level 7, tone 3 | A medium blonde with a gold / golden primary reflect |
| 6/1 | Level 6, tone 1 | A dark blonde with an ash primary reflect |
| 8.34 | Level 8, tone 3, secondary 4 | A light blonde, gold primary with a copper secondary |
| 5N or 5.0 | Level 5, natural | A light brown with a neutral base, no added reflect |
The level digit is your anchor. It is the piece you trust most when crossing brands. The tone digits are the negotiation, because that is where two systems genuinely disagree about what a number means.
The defensible conversion method, step by step
Here is the workflow that holds up when a chart fails you. It assumes you already understand level, tone, developer, and your own ratios.
1. Decode the source formula into level and tone
Strip the formula down to its plain-language meaning before you touch the new brand. Write it as: target level, primary reflect, any secondary reflect, plus the developer volume and ratio that were used. A "6.43 with 20 volume at 1:1" becomes "level 6, copper-gold, lifted with 6% at equal parts." Now you are working in a language every brand shares, not in one brand's catalogue numbers.
2. Match the level exactly, then the tone family
In the new line, find the shade that sits at the same level and lands in the same tone family: ash to ash, gold to gold, copper to copper, neutral to neutral. Do not chase the exact tone digit, because the digits will not line up. Match the family and the intensity instead. If the source was a soft gold, do not jump to the new brand's most intense gold just because the number looks similar.
3. Keep your developer and ratio constant for the test
Change one variable at a time. Use the same developer volume and the same color-to-developer ratio the original formula used, so the only thing you are testing is the shade swap itself. If you change the brand, the developer, and the ratio all at once and the strand comes out wrong, you will not know which decision caused it.
4. Strand-test, and judge against the right starting point
Process a strand on hair that reflects the client's current condition, level, porosity, and history, then evaluate it dry and in good light. The strand tells you what the conversion actually does on this hair, which no chart can predict. Underlying warmth, porosity, and prior color all change the outcome, and the chemistry review is blunt about this: the result is built inside the strand by the reaction, not assigned by the label.
5. Record what it became, not just what you intended
This is the step that separates a reliable colorist from a lucky one. Write down the converted formula and, next to it, the actual result of the strand: too warm, half a level dark, perfect at the roots but pulling brass on the ends. The conversion is only the first attempt. The recorded result is what makes the second attempt informed instead of another guess.
Where charts are useful, and where they lie
A cross-brand chart is a fast way to generate a same-level, same-family candidate so you are not scanning a swatch book blind. That is real value. The lie is in the word "equivalent." No published chart can account for your client's hair history, the porosity of color-treated ends, how a given base fades over six weeks, or how two lines handle gray coverage at the same level. Use the chart to narrow the search; use the strand and your record to make the decision.
How Color Formula handles cross-brand conversion
Color Formula is built around this exact trust boundary. It compares shade-family starting points within a level-and-tone framework, so you can line up a same-level, same-family candidate in the brand you are moving to. It does not pretend the result is an identical match. Cross-brand conversions are labeled as starting points to test, not guaranteed equivalents, which is the honest version of what a conversion chart should be.
The part that makes it pay off is the record. A starting point is only useful if you capture what it became. Color Formula stores the converted formula alongside the developer, ratio, and the actual strand result, so your second attempt starts from evidence instead of memory. The next time you switch a client between lines, you are reading a recorded outcome, not re-running the same hopeful guess.
Color Formula compares shade-family starting points within a level-and-tone framework, labels cross-brand conversions as starting points to test, and stores the actual result so your second attempt is informed. On-device, no account.
Coming soon to the App Store.Frequently asked questions
Is there a chart to convert hair color between brands?
Charts exist, but none of them produce a guaranteed identical result. They are useful as a way to find a same-level, same-tone candidate in the new line. Pigment load, base tone, and how each brand reads its tone digits all differ, so the chart gives you a defensible starting point to strand-test, not a finished formula.
How do I read a hair color number across brands?
Read the first digit as the level on the universal 1-10 scale (1 is black, 10 is lightest blonde) and the digits after the dot or slash as the tone or reflect. A 7.3 and a 7/3 both mean a level 7 with a gold reflect. The level travels across brands fairly reliably; the tone digits are where systems diverge, because each line assigns its own number to ash, gold, copper, and so on.
Why does the same level look different in two brands?
Because two tubes at the same level can carry different amounts and kinds of pigment. Permanent color deposits oxidative dye while peroxide lifts the natural melanin underneath, and brands load their bases differently for coverage, warmth control, and fade behavior. Same level, different pigment recipe, different result on the head.
Do I still need to strand-test a converted formula?
Yes. A conversion is a hypothesis about which shade in the new brand sits in the same level-and-tone family. The only way to know how it lifts, deposits, and fades on this client's hair history and porosity is to test a strand and record what it actually became. Skipping the test is how a confident conversion turns into a correction appointment.
What is the safest way to switch a client to a new color line?
Anchor on the client's current level and target level, find the same-level, same-tone-family shade in the new brand, strand-test it at your normal developer and ratio, then log what the strand turned out to be. Adjust tone or developer on the second attempt from a recorded result instead of from memory. That recorded second attempt is what makes the switch reliable.
Keep reading
Sources
- Comprehensive Review of Hair Dyes (ACS Omega, via NCBI / PMC), oxidative dye chemistry, the role of peroxide in lifting melanin, and how precursor concentration changes the shade.
- Wella Professionals, Koleston Perfect and Illumina Color use the level.tone shade-numbering convention referenced here.
- L'Oreal Professionnel, Majirel shade numbering, level followed by primary and secondary reflect.