Hobby · Painting and airbrushing
Airbrush paint thinner ratio calculator.
Enter a ratio in whichever notation your source uses and the calculator turns it into millilitres of paint and thinner for your cup, and shows the same mix in the other two notations. The notation is the catch: one forum poster starts at 1.5:1 thinner to paint, which is 60% thinner, while a guideline quoted for Tamiya acrylics is 2:1 to 3:1 paint to thinner, which is 25% to 33%. Example: 2:1 paint to thinner in a 6 ml cup is 4 ml paint and 2 ml thinner.
Your numbers
Result
Working out the result.
How the paint and thinner volumes are calculated
Every notation reduces to one number: the thinner fraction, thinner divided by paint plus thinner. Paint to thinner of 2:1 is 1 ÷ 3 = 33.3% thinner. Thinner to paint of 2:1 is 2 ÷ 3 = 66.7% thinner, the opposite mix. A percentage is used as given. The page multiplies your cup volume by that fraction for the thinner and by one minus it for the paint, and for paint you already have it adds paint × fraction ÷ (1 − fraction) of thinner.
The ratios themselves are not ours. Tamiya’s enamel product page states that when spray painting enamels the best results come from “adding 2 parts of thinner to 10 parts of paint,” which is 1:5 or 16.7% thinner. For acrylics, a poster in a FineScale Modeler thread quoted “Rough guidelines of thinning ratio is 2:1-3:1 (Tamiya Acrylic paint : thinner),” and other posters reported what works for them. None of these is a specification for your paint, airbrush, pressure or weather, so the table below lists them as starting points to test on scrap plastic.
Starting points people report
| Source | As written | Thinner share |
|---|---|---|
| Tamiya enamel product page (the maker) | 2 parts thinner to 10 parts paint | 16.7% |
| Forum poster quoting a Tamiya acrylic guideline | 2:1 to 3:1 paint to thinner | 25.0% to 33.3% |
| Forum poster, lacquer thinner (standard coverage; filters 9:1) | 1.5:1 thinner to paint | 60.0% (filters 90.0%) |
| Forum poster, X-20A thinner at 16 to 20 psi (detail work 1:1 at about 12 psi) | 2 parts paint to 1 part thinner | 33.3% (detail 50.0%) |
| Forum poster, lacquer thinner at about 20 psi (translucent layers 50:50) | about 70% paint, 30% thinner | 30.0% (translucent 50.0%) |
| Forum poster advising where to start | start at 50/50 | 50.0% |
Worked examples with real numbers
- 2:1 paint to thinner, 6 ml cup. 33.3% thinner: 4.0 ml paint and 2.0 ml thinner.
- Tamiya enamel, 2 parts thinner to 10 of paint, 6 ml cup. 16.7% thinner: 5.0 ml paint and 1.0 ml thinner.
- 1.5:1 thinner to paint, 6 ml cup. 60% thinner: 2.4 ml paint and 3.6 ml thinner.
- 5 ml of paint poured, aiming for 2:1 paint to thinner. Add 2.5 ml of thinner.
- Too much thinner. With 2 ml paint and 4 ml thinner (66.7% thinner), reaching 33.3% needs 6 ml more paint.
What this calculator leaves out
It does not know your paint, thinner type, nozzle, pressure or humidity, all of which posters in the threads say matter: one uses about 70% paint to 30% thinner for basecoats at around 20 psi and 50:50 for translucent layers at 15 to 18 psi, and notes that temperature and humidity matter. It does not include flow improver, retarder or drops, since no amounts could be verified. Thinner type also matters; acrylic thinner, lacquer thinner and isopropyl alcohol are not interchangeable with every paint. Test on scrap and read your paint maker’s own instructions. See the paint mixing ratio calculator for general colour recipes by parts.
Common mix-ups
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Often assumedA ratio of 2:1 always means two parts paint to one part thinner.
What the source saysIn one forum thread a poster starts at 1.5:1 thinner to paint (60% thinner), while another quotes a Tamiya acrylic guideline of 2:1 to 3:1 paint to thinner (25% to 33% thinner). The notation runs in opposite directions. [1]
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Often assumedTamiya publishes one ratio for all its paints.
What the source saysTamiya’s enamel page gives 2 parts of thinner to 10 parts of paint for spraying enamels. The acrylic figures in the thread are posters’ reports, and one poster quotes the guideline without a link. [2] [1]
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Often assumedThinning is about hitting a number.
What the source saysSeveral posters say to thin to about the consistency of milk, and one advises testing on a primed model, because bottles and conditions vary. [1]
Checked against these sources on .
Frequently asked questions
What is the ratio of paint to thinner for an airbrush?
There is no single ratio. Tamiya states 2 parts thinner to 10 of paint for spraying its enamels. For acrylics, forum posters report anything from 2:1 paint to thinner to 1.5:1 thinner to paint, depending on paint, pressure and weather.
Is 2:1 paint to thinner the same as 2:1 thinner to paint?
No, they are opposites. 2:1 paint to thinner is 33% thinner; 2:1 thinner to paint is 67% thinner. Check which way a source writes it before you pour, and use the notation selector here.
How much thinner do I add to 5 ml of paint?
Multiply the paint by the thinner fraction over one minus the fraction. For 2:1 paint to thinner that is 5 × 0.333 ÷ 0.667 = 2.5 ml. Enter your paint volume in the optional box.
What consistency should airbrush paint have?
Several posters in the FineScale threads describe thinning to about the consistency of milk (one says “2% milk”) rather than to a fixed ratio, and one advises testing on a primed model.
Can I use water or alcohol to thin Tamiya acrylics?
Posters report using Tamiya X-20A, lacquer thinner and isopropyl alcohol, with differing results, and one said most people thin with water for detailed work. Follow your paint maker’s instructions, because this page only does the volume maths.
How do I fix a mix that is too thin?
Add paint. If the cup holds 2 ml of paint and 4 ml of thinner and you want 2:1 paint to thinner, add 6 ml of paint. If you do not have that much, use a smaller target amount instead of keeping the whole cup.
Sources
Retrieved
- Tamiya: enamel paint product page — “when spray painting enamels, best results are achieved by adding 2 parts of thinner to 10 parts of paint” (read 2026-10-26)
- FineScale Modeler forum: Ratio of Tamiya paint to thinner — posters report 1.5:1 thinner to paint, 2 parts paint to 1 part X-20A, 70/30 and 50/50 mixes; one quotes a 2:1 to 3:1 paint to thinner guideline for Tamiya acrylics (read 2026-10-26)
- FineScale Modeler forum: Thinning Tamiya Color acrylic paint — posters report 2:1 paint to thinner, 50/50 mixes and thinning to the look of 2% milk; no official Tamiya guideline is quoted (read 2026-10-26)
Volume maths, not a paint specification
Not affiliated with Tamiya or any paint maker. The ratios listed are as reported by the sources named and as read on 26 October 2026; test on scrap before spraying a model. Nothing you type is sent or stored.