The direct answer for 400 mL of paint
At 4:1, 400 mL paint takes 100 mL hardener. Then:
- 10% of paint alone: 40 mL reducer, giving 540 mL finished mixture.
- 10% of paint + hardener: 50 mL reducer, giving 550 mL finished mixture.
Both calculations are mathematically correct for their stated basis. The product’s instructions determine which one applies. These are arithmetic examples, not mixing recommendations for an unspecified paint.
Why “4:1:1” is a different recipe
In a three-part volume ratio, all three numbers are component parts. At 4:1:1, 400 mL paint takes 100 mL hardener and 100 mL reducer, making 600 mL total.
That 100 mL reducer equals 25% of paint, 20% of paint + hardener, or about 16.67% of the final mixture. A percentage has no complete meaning until its denominator is specified.
| Instruction | Hardener | Reducer | Final amount |
|---|---|---|---|
| 4:1 + 10% of paint | 100 mL | 40 mL | 540 mL |
| 4:1 + 10% of paint + hardener | 100 mL | 50 mL | 550 mL |
| 4:1:1 component parts | 100 mL | 100 mL | 600 mL |
Starting with a desired finished amount
If your technical sheet specifies 4:1 plus 10% of the combined paint-and-hardener volume, and you want 550 mL finished mixture, first divide by 1.10: 550 ÷ 1.10 = 500 mL activated mixture. Split that 500 mL into five parts: 400 mL paint + 100 mL hardener, then add 50 mL reducer.
For a 10% addition to paint alone, the scale factor is different. With 4 paint parts, 1 hardener part and 0.4 reducer parts, there are 5.4 total parts. Divide your final amount by 5.4, then multiply by 4, 1 and 0.4 respectively.
Find these details on the technical sheet
- The exact paint, compatible hardener and reducer.
- The paint-to-hardener ratio and whether it is by volume or weight.
- What the reducer percentage is calculated against.
- Any application-dependent permitted addition, mixing order and limits.
If the percentage basis is absent or ambiguous, confirm it with the manufacturer. Optional thinning instructions can be separate from the base/activator ratio, as illustrated by KBS MAXX manufacturer directions. That reference is context, not a 4:1 preset or permission to use its instructions for another product.
Calculate using your own instructions
For a hardener-plus-percentage recipe, select Paint + hardener + reducer below. Choose the percentage basis stated by your product, then enter its ratio and amount.
Can I weigh these amounts instead?
A ratio by volume does not automatically become the same ratio by weight. Use the manufacturer’s weight ratio or exact component densities as appropriate. The known-ingredient mixer supports an explicitly supplied weight ratio; the paint chart builder makes repeatable volume-reference charts from your entered recipe.