The Logic Behind the Calculator

What you tell it

Six inputs describe where your hair is now and where you want it to go.

• Current level — how dark or light your hair is today
• Current tone — the warmth already in the hair
• Target level — the depth you want
• Target tone — the direction you want to take it
• Previously bleached or lightened — this changes how hair takes color
• Gray percentage — how much of the hair needs coverage

What you get back

A complete formula, not a set of vague instructions.

• The shade code to mix, written the way colorists write it (7A = level 7 ash)
• The developer to use with it
• Any toner, filler, natural base or corrector the change calls for
• Processing time
• Application steps in order
• A risk rating, so you know what you are taking on
• Warnings and notes specific to your hair
• An alternative route where a second approach makes sense

Hair levels

Hair is measured on a level scale from 1 to 10. Level 1 is the darkest black; level 10 is the lightest pale blonde. Your natural hair sits somewhere on this scale, and every formula targets a point on it.

The distance between where you are and where you want to be is the most important number in the calculation. It decides whether you are lightening, staying at the same depth, or darkening — and how much the hair has to do to get there.

Tone and neutralization

Unwanted warmth is cancelled by its opposite on the color wheel. Yellow, orange and red each have a counter-tone that neutralizes them, and the calculator applies the right one for your hair — but only when your goal is cool or balanced. If you are heading warm, that warmth works in your favour and stays.

Lightening also exposes pigment that was not visible before, so the formula accounts for warmth you have yet to see, not only the warmth that is there now.

Hair condition and gray

Previously lightened hair behaves differently from virgin hair, and gray hair has no pigment to build on. Both change what a formula needs to hold and look right. Telling the calculator about them is what separates a formula that works from one that turns hollow, flat or patchy.

Checkpoints

Hair rarely lands exactly where theory says it should. Larger changes are returned with checkpoints built in — points where you stop, look at what you actually have, and continue from there.

If the result differs from the plan, run the calculator again using what you see as your new starting point. You get a fresh formula for the next step.

Why it is rule-based

Every result comes from a fixed rule, not a guess. The same inputs always return the same formula, and the reasoning traces back to standard color theory.

Formulas are generic and brand-neutral — a shade code, a developer, and a supporting product where one is needed. You use the line you already trust and match it to the formula.