Model Paint Thinning Ratio Calculator
Work out exactly how much thinner to add to hobby acrylic paint for brush or airbrush work, in drops and millilitres.
How it works
thinner = paint × ratio · total = paint + thinner · ratio = parts thinner per 1 part paint
Hobby acrylics come thick and almost always need thinning, but the right amount depends entirely on how you apply it. Brush layering wants only a splash so paint still covers; airbrushing wants a milk-like consistency around 1:1; washes are mostly medium so pigment flows into recesses. Working in drops keeps ratios repeatable regardless of batch size — the ratio is what matters, not the absolute volume — so you can mix a test amount and scale it up once the consistency is right.
Worked example
For general airbrushing at a 1:1 ratio with 10 drops of paint: thinner = 10 × 1 = 10 drops, for 20 drops total (about 1 ml), a milk-like consistency.
Frequently asked questions
What should I thin with?
Manufacturer airbrush thinner or a proper acrylic thinner is safest. Distilled water works in a pinch but can weaken adhesion and flow at high dilutions; flow improvers and retarders fine-tune behaviour without over-thinning.
How do I judge the right consistency?
Aim for milk for general airbrushing and skim milk for fine lines. On a brush, thinned paint should flow off the tip smoothly without being transparent in one coat.
Can I over-thin paint?
Yes — too much thinner breaks coverage, causes tip-drying to look like grain, and can pool or run. If a coat goes translucent or watery, add a drop of paint back into the mix.
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This calculator is for educational purposes. Double-check important results before acting on them.