Dye Calculator
Enter your fabric weight and dye type to get the correct dye, water, and salt ratios.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Getting the dye ratio right is the key to consistent color results. Too little dye produces a washed-out shade; too much wastes dye without improving color. This calculator gives you the correct amounts for each dye type.
- Weigh your dry fabric. Weigh the fabric before getting it wet — wet fabric weighs more. Use a kitchen scale. The standard unit for dye calculations is dry fabric weight in ounces or pounds.
- Select your dye type. Rit powder and liquid are all-purpose dyes that work on most natural fibers and nylon. Fiber reactive (Procion MX) dyes cellulose fibers (cotton, linen, rayon) permanently with vibrant colors. Acid dyes are for protein fibers (wool, silk, alpaca).
- Choose your shade. Light shade uses less dye. Dark shade uses more. Medium is the standard amount listed on most dye packages.
- Follow the results. The calculator gives you the dye amount, water, salt (to help the dye absorb), and soda ash (for fiber reactive dyes only, used as a fixative).
About the Dye Calculator
Dye amounts are based on manufacturer recommendations and standard dye house practices. Rit powder: 1/3 oz packet per pound of dry fabric for medium shade. Rit liquid: 1/2 bottle (about 4 fl oz) per pound. Fiber reactive dyes follow the "depth of shade" system: light is 1% of fabric weight in dye powder, medium is 2%, dark is 4%. Salt acts as a leveling agent, helping the dye distribute evenly. Soda ash (sodium carbonate) is a fixative for fiber reactive dyes, raising the pH to permanently bond the dye to cellulose fibers. Always add soda ash after the fabric has been in the dye bath for 20–30 minutes.
Frequently Asked Questions
How much Rit dye do I need for a pound of fabric?
For a medium shade with Rit powder dye, use one packet (about 1/3 oz) per pound of dry fabric. For a darker shade, use one and a half packets. For Rit liquid, use 1/2 bottle (about 4 oz) per pound of fabric for medium shade. The calculator scales these amounts for any fabric weight you enter. A typical cotton shirt weighs about 6–8 oz dry, so half a packet of Rit powder is usually enough for a medium-shade result.
What is the difference between fiber reactive and all-purpose dye?
All-purpose dyes like Rit work on most fibers including cotton, linen, nylon, and blends, but the colors can fade over time, especially with frequent washing. Fiber reactive dyes (like Procion MX) form a permanent chemical bond with cellulose fibers (cotton, rayon, linen), producing bright, wash-fast colors that do not fade. Fiber reactive dyes require a fixative (soda ash) and work cold or warm. They do not work on synthetic fibers. For long-lasting results on 100% cotton, fiber reactive is the professional choice.
Why do I need to add salt when dyeing fabric?
Salt acts as a leveling agent and exhaustion aid. In dyeing, "exhaustion" means how much dye transfers from the water to the fiber. Salt creates a mild ionic competition that slows the initial dye uptake, allowing the dye to distribute more evenly before it bonds permanently. Without salt, fiber reactive dyes can produce uneven, blotchy results, especially on larger pieces. For acid dyes on wool, vinegar is used instead of salt to lower the pH and help the dye bond.
How do I weigh fabric if I do not have a scale?
A kitchen scale is the most accurate option. If you do not have one, use reference weights: a standard cotton t-shirt weighs about 6–8 oz (170–225g), a pair of jeans weighs about 20–24 oz (560–680g), a cotton pillowcase weighs about 4–6 oz, and a yard of quilting cotton (44" wide) weighs about 4–5 oz. Use these as rough guides when estimating, then round up on your dye amount to ensure full color saturation.