How to write down a hair color formula

A good formula note lets you repeat a color six weeks later without guessing, and lets anyone covering for you do the same. Here is what to write down, how to write it, and a few examples.

What to write down

The starting point: natural level, how much gray, and anything left from past color. Note allergies and the date of the last patch test too.
The date of the visit and the service.
Each shade with its amount, in grams or parts, and the brand and line.
The developer volume and the mixing ratio.
Where each mix went: roots, mids and ends, or each section, when they get different mixes.
Timing: how long each mix processed, and whether you used heat.
Toner or gloss, with its own developer and time.
The result, and what to change next time.

How to write it

Shades: the level first (1 is black, 10 the lightest blonde), then the tone. Some lines use letters, like 7A for an ash 7 or 6N for a natural 6. Others use numbers after a slash or a dot, like 7/1 or 7.1, and those tone numbers differ between brands. That's why the brand goes on the note.
Amounts: grams are the most exact (6N 30g + 7G 10g). Parts work too (6N + 7G, 3:1) when you always mix the same total.
Developer: write the volume, or the percentage if that's what's on your bottle. 10 vol is 3%, 20 vol is 6%, 30 vol is 9% and 40 vol is 12%.
Ratio: color to developer, like 1:1 or 1:1.5. Lighteners are often 1:2.
One line per mix, starting with where it went: "Roots:", "Ends:", "Toner:".

Examples

Gray coverage

Roots: 6N 40g + 6G 20g, 20 vol 1:1, 45 min

Result: full coverage at the temples. Same next time.

Root touch up and gloss

Roots: 6N 30g + 7G 10g, 20 vol 1:1.5, 35 min

Gloss: 9V + clear 1:1, 10 min

Result: a little warm at the part. Next time add 5g 6A.

Balayage

Lightener 1:2, 20 vol, open air, 40 min, lifted to a 9

Toner: 9A + 9V 1:2, 10 vol, 20 min

Result: even, a touch yellow at the ends. Next time leave the ends 5 min longer.

Tips that make a formula useful later

Write it while you mix, not at the end of the day.
Use exact amounts. "A bit of 7G" means nothing six weeks later.
Write a new note each visit instead of changing the old one, so you can see how the formula changed.
Take a photo of the result, in daylight if you can.
Write what you'd change while it's fresh: "a bit cooler", "lift less at the part".

Keeping formulas in HairSync

HairSync is salon booking software built for stylists: the calendar, the clients and their formulas in one place. Each visit can get its own note with a formula field, a photo, the price and the time it took. The formula is plain text, so you write it as above, with any brand. Next time, search the client by name or phone and their visits are listed newest first, so anyone in the salon can mix it again.

It runs in the browser on your phone, tablet or laptop, with no app to install, and costs $20 a month per stylist with text reminders included. It's free for up to 100 clients.

Start free

No credit card required.