Always follow the manufacturer’s maximum thinning guidance, because over-thinned paint covers poorly.
How to scale a paint recipe
A colour recipe is a list of parts: two parts yellow, one part blue, three parts white. Parts are a ratio, so they work for a thimble or a bucket. To turn them into amounts, add up the parts (here six), divide the batch size by that number, and multiply by each colour’s parts. For 600 ml, one part is 100 ml, so you need 200 ml yellow, 100 ml blue and 300 ml white. PaintRatio does this for every row as you type and shows each colour’s share as a percentage.
Volume or weight?
Either is fine as long as you use the same unit for every component. Weight on a kitchen or jewellery scale is more accurate for thick acrylics, oils and resin, and avoids paint clinging to measuring cups. For tiny miniature-painting amounts, drops from a dropper bottle work well as a unit.
Matching a colour you already mixed
If you mixed by eye and measured afterwards, enter the amounts in the ratio finder and it reduces them to the simplest whole-number ratio, which you can load as a recipe. When you run short halfway through a wall, enter how much of the first colour you have left and the calculator tells you how much of the others to add, so the second batch matches the first.
About the colour preview
Paint mixes subtractively: each pigment absorbs part of the light, so mixing darkens and shifts colours in ways that screen colour mixing does not. The preview uses a simple subtractive model, which gets the direction right, such as blue and yellow making green, but cannot know the exact pigments in your tubes. Treat it as a planning aid and always paint a test swatch. Tints add white and shades add black to show how far the colour can stretch.
Two-part products
Epoxy resin, two-part polyurethane and some primers must be mixed at the ratio on the label to cure properly. Check whether the ratio is by weight or by volume, mix thoroughly, scraping the sides, and only make as much as you can use within the working time.
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Frequently asked questions
What is a typical thinning ratio for a sprayer?
Often around 10% thinner for latex in an HVLP sprayer, but it varies; check the paint label.
Water or mineral spirits?
Water for water-based paints; the solvent named on the can for oil-based paints.
How do I test it?
Use a viscosity cup or check that the paint drips smoothly off a stir stick.
Is PaintRatio free?
Yes, with no sign-up.
Is my data private?
Recipes are saved only in this browser.