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How fabric dye ratios work
Immersion dyeing colours fabric by soaking it in a dye bath, and the depth of colour depends on a simple ratio: the weight of dye compared with the dry weight of the fabric, shown as a percentage called depth of shade. A light shade uses about one percent dye, meaning one gram of dye for every one hundred grams of fabric. A medium shade uses about three percent, and a dark shade uses about six percent or more. This ratio is why weighing matters: two pieces of fabric that look similar can weigh very differently, and dyeing by eye or by spoon gives uneven, unpredictable colour. Weighing the dry fabric first, then calculating dye from that weight, is the professional habit that gives repeatable results.
Water amount matters just as much as dye amount. The liquor ratio is the weight of water compared with the weight of fabric, and a common home ratio is 1:20, meaning twenty grams of water, about twenty millilitres, for every gram of fabric. A 200 gram shirt therefore needs about four litres of water. Too little water crowds the fabric, so dye cannot reach every fibre evenly, and the result is patchy. Too much water dilutes the dye and wastes salt and helpers, though it rarely harms the colour if the dye amount is right. This calculator gives dye weight, water volume at 1:20, and a salt guide, so you can set up the bath correctly before the fabric goes in.
How to use the dye ratio calculator
Weigh your fabric completely dry, in grams, before washing or wetting it, because wet fabric weight includes water and would inflate every calculation. Choose the depth of shade you want, from light to very dark, and the tool gives the dye weight in grams, the water in litres, and a salt guide of fifty grams per litre of water. For example, 200 grams of fabric at a medium three percent shade needs six grams of dye, four litres of water, and about two hundred grams of salt. Dissolve the dye fully in warm water before adding it to the bath, add the salt dissolved as well, and stir well so no undissolved grains sit on the fabric and cause spots.
Always follow your dye maker’s instructions for helpers, because different dye types need different chemistry. Fibre reactive dyes for cotton and linen usually need soda ash to fix the colour, while acid dyes for wool and silk need vinegar or citric acid and heat. Salt helps dye move onto the fibre, but the amount and timing vary by dye type, so treat the salt figure here as a guide, not a rule. If your dye maker gives a different salt amount, follow theirs. Dye in a pot large enough for the fabric to move freely, stir gently and often, and keep the bath at the temperature your dye maker specifies.
Fabric type changes everything
Natural fibres dye well, while synthetics often resist. Cotton, linen, rayon, wool, and silk take dye readily, though each needs its matching dye type. Polyester and most synthetic blends need special disperse dyes and high heat, and home dyeing often gives pale, uneven results on them. Blends dye unevenly by design: a cotton-polyester shirt dyed with cotton dye will colour the cotton fibres and leave the polyester fibres pale, giving a heathered look that some makers love and others hate. Always check the fabric label, dye a test swatch first, and never dye a garment you cannot afford to lose on the first attempt with a new dye or fabric.
Getting even colour
Even colour comes from movement, not from more dye. Wet the fabric thoroughly before it enters the bath, so dye soaks in evenly instead of grabbing dry patches first. Stir slowly and continuously for the first ten minutes, then regularly afterwards, lifting and turning the fabric so no fold stays hidden. Keep the fabric loose in the pot: if it is packed tight, the outer layers dye dark and the inner layers stay pale. After dyeing, rinse in cool water until the water runs mostly clear, then wash with a mild detergent in warm water to remove unfixed dye. The first wash may release some colour, which is normal, so wash dyed items separately the first few times.
Common dye mistakes
The most common mistake is dyeing wet fabric by its wet weight, which overstates the fabric weight and leads to too much dye and a darker result than planned. The second is using too little water, which causes patchiness that no amount of stirring fixes. The third is adding dye powder directly to the pot, which causes speckles where grains land on fabric. The fourth is skipping the test swatch, so a whole garment becomes the test. Avoid all four by weighing dry, using the calculated water volume, dissolving dye first, and testing a swatch. With those habits, plus this calculator for the ratios, immersion dyeing becomes predictable, repeatable, and genuinely enjoyable.