What ratio should I mix bleach powder with developer?

The standard ratio is 1:2 (one part powder to two parts developer), which gives a creamy, workable consistency. Some brands recommend 1:1.5 or 1:3 — always check the product instructions. A thicker mix (more powder) stays in place better for highlights and foils.

How long can bleach be left on hair?

Never exceed 45 minutes processing time. Most bleach reaches maximum lift within 30-45 minutes. After that, you are only causing damage without further lightening. If more lift is needed, rinse, condition, and re-apply in a second session.

Should I use 20 or 30 volume developer with bleach?

20 vol provides slower, gentler lightening (ideal for finer hair or on-scalp work). 30 vol is stronger and processes faster. Use 20 vol for scalp bleach and 30 vol for off-scalp techniques like foils and balayage. 40 vol is rarely necessary and increases damage risk significantly.

Why does my bleach swell in the bowl?

Bleach swells because it releases oxygen gas during the chemical reaction. This is normal. A small amount of swelling indicates the product is active. Excessive swelling may mean you used too much developer or the environment is too warm. Mix in a well-ventilated area.

CutCalcs

Bleach Mix Calculator — Powder & Developer Quantities

Calculate bleach powder to developer ratios and total quantities for lightening services.

Hair Length

Technique

Mixing Ratio

Developer Volume

How We Calculate This

This calculator estimates the total bleach powder and developer quantities based on hair length, technique and your chosen mixing ratio.

The formula

Powder amount = Base amount x Technique multiplier

Developer amount = Powder x Developer ratio

Full head: 100% of base amount
Highlights: 50% of base amount
Balayage: 60% of base amount
Roots only: 30% of base amount

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always perform a strand test before chemical services.