Thinning Ratio Calculator — Paint to Thinner

This calculator splits your total cup volume into paint and thinner using the selected ratio: paint = total × paint-parts ÷ (paint-parts + thinner-parts). The figures below are starting points — your exact ratio depends on nozzle size, air pressure and paint batch, so always test on scrap first.

Common ratios (paint:thinner)

• Acrylic airbrush: 1:1 to 1:2 (Tamiya X-20A guidance is ~1:1, adjust to a skimmed-milk flow)
• Acrylic brush: just a few drops of thinner per pot, if any
• Enamel airbrush: ~2:1 (Humbrol airbrush guidance: 1–2 parts paint to 1 part Enamel Thinner)
• Lacquer airbrush: ~1:2, but commonly thinned further. Tamiya/Mr Color lacquers are often run anywhere from 1:1 to 1:4 paint:Levelling Thinner depending on the job — start at 1:2 and adjust.

Aim for the consistency of skimmed milk: it should run off a stirrer smoothly and lay down on test plastic without spattering, pooling or orange-peel. The optional Retarder field substitutes part of the thinner with a flow retarder to slow drying (handy for fine lines and hot conditions) — Tamiya retarder is typically used sparingly, around 1 part to 10 of paint.