Hair dye
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For long hair (below the shoulder), plan on 2 boxes for medium-thickness hair. If your hair is thick or coarse, get 3 boxes. For very long hair reaching mid-back or beyond, 3 boxes is the minimum regardless of thickness — you can always return an unopened box. Our box calculator above gives you a precise number based on your exact length, thickness, and texture.

Short hair (2–4 inches) typically needs just 1 box of hair dye. A pixie cut uses even less — about half a box. The exception is very thick short hair, where you may need 1.5 boxes. Most people with short hair waste half a box every session — use the leftover to do a strand test first or touch up roots between full applications.

The standard ratio is 1:2 — one part bleach powder to two parts developer. For shoulder-length medium-thickness hair doing a full application, you need about 1.5 oz bleach and 3 oz developer (4.5 oz total). Thick hair needs 25–50% more; fine hair needs 25% less. Never mix bleach by volume — always weigh it on a kitchen scale for consistent results.

Most box dyes include a pre-measured developer, typically 20 volume (6% peroxide). This is the standard for permanent color and covers gray while lifting 1–2 levels. If your box dye includes the developer already, don't add extra. If you're buying developer separately, use 20 volume for standard coloring, 30 volume if you need 2–3 levels of lift, and 10 volume for toning or going darker.

Yes — mixing two permanent shades gives you a custom blended color. Combine equal parts of each shade for a 50/50 mix, then add developer based on the combined color amount using your product's ratio (typically 1:1 for permanent color). The result is an average of the two shades. Always do a strand test first since mixed colors can behave unpredictably on different base colors.

Most people save $500–$1,500 per year by coloring at home instead of visiting a salon. A typical salon single-process color costs $80–$150 plus tip, while DIY costs $10–$30 per session. If you color every 6 weeks, that's roughly 9 sessions per year — the savings add up fast. Use our DIY vs Salon calculator above to see your exact numbers.

Permanent hair dye lasts until it grows out, but the color fades with each wash. Most permanent colors maintain vibrancy for 4–6 weeks before fading noticeably. Darker colors last longer than lighter ones. To extend longevity: use sulfate-free shampoo, wash in cool water, use color-protecting conditioner, and limit washing to 2–3 times per week.

Most permanent box dyes process in 25–45 minutes depending on the brand and desired result. Demi-permanent color takes 20–30 minutes. Never leave permanent dye on longer than the instructions state — extra time doesn't improve color and can cause dryness and damage. For gray coverage, the full recommended time is usually necessary.