The paint mix ratio guide
Read the ratio.
Know what the total includes.
A base:additive ratio can be simple arithmetic and still be easy to misread. The main question is whether your starting amount is the base alone or the combined total. The other is what a percentage is a percentage of.
Define the order and the measurement basis
Every ratio in this tool reads base : additive, by volume. In 4:1, the first component receives four equal-volume parts and the second receives one. A “part” has no fixed size: it may be 10 mL, 200 mL or another volume, provided both components use the same unit and the same part size.
That is different from a ratio by mass. Liquids can have different densities, so a volume ratio cannot be transferred to a scale by keeping the same numbers. This tool has no density inputs and does not calculate weight. It also does not interpret three-part instructions or reverse a label’s component order automatically.
Starting point one: you want a combined total
Let B be base parts, A additive parts and T your desired arithmetic total. There are B + A equal parts altogether:
Base volume = T × B ÷ (B + A)
Additive volume = T × A ÷ (B + A)
For the labelled arithmetic example, use 4 parts base and 1 part additive with a desired total of 1,000 mL. Five equal parts make up that total, so one part is 200 mL. Base is 4 × 200 = 800 mL and additive is 1 × 200 = 200 mL. Their arithmetic sum is 1,000 mL.
The entered total already includes the additive. Starting with 1,000 mL of base and adding 250 mL would produce a different total, even though the component ratio would still be 4:1.
Starting point two: the base amount is known
If you already know the base volume V, scale the additive relative to it:
Arithmetic total = V + additive volume
With the same illustrative 4:1 ratio and 1,000 mL of base, additive is 1,000 × 1 ÷ 4 = 250 mL. The arithmetic total is 1,250 mL. Neither starting mode is more accurate by itself; choose the one that matches what the number in your hand actually represents.
| 4:1 example | Base | Additive | Arithmetic total |
|---|---|---|---|
| Desired total: 1,000 mL | 800 mL | 200 mL | 1,000 mL |
| Known base: 1,000 mL | 1,000 mL | 250 mL | 1,250 mL |
Why 25% of base is 20% of final
“Add 25%” is incomplete unless the reference amount is clear. At 4:1, additive divided by base is 1 ÷ 4, or 25%. Additive divided by the complete five-part total is 1 ÷ 5, or 20%.
Additive percentage of final total = A ÷ (B + A) × 100
For a direction explicitly stating an additive percentage p of base volume, the corresponding arithmetic ratio is 100:p. If the percentage explicitly refers to the final combined volume, its ratio is (100 − p):p, with p below 100. These conversions only interpret wording; they do not establish that adding the material is permitted. Resolve ambiguous label wording with the supplier before using a number.
Do not turn the example into a thinning recommendation
The example is deliberately a ratio exercise, not a product recipe. Paint directions can differ. For instance, the application instructions for Dulux Wash&Wear +PLUS Anti-Scuff Low Sheen say thinning is generally unnecessary. That product page is a reason to check the actual instructions, not a basis for applying its directions to other paints.
The tool cannot know which liquid your “additive” represents. It could not determine compatibility, permitted amounts, the need to use complete supplied packs, measurement equipment, ventilation, application settings or usable working time from a numerical ratio. Those remain product-specific matters outside this volume calculation.
Units and rounding
Choose millilitres or litres for the number you enter. One litre is 1,000 millilitres, and the component results also show mL for comparison. Changing the selected unit reinterprets the entered number rather than silently converting it: 1,000 mL and 1,000 L describe different amounts.
The accepted input decimals are retained exactly in the ratio arithmetic. Display values are rounded and marked ≈ when necessary. A ratio of 2:1 and a total of 1 L, for example, produces repeating component values: approximately 0.667 L and 0.333 L. The underlying fractions still sum to 1 L; display rounding is not a measurement instruction.
The maximum input of one billion and the resulting-total limit are software bounds, not recommended batch sizes. The tool accepts zero additive for the mathematical case of base alone. Base parts, the known amount and the desired total must be positive. Scientific notation, negative values and unit words pasted into number fields are rejected so the displayed units remain unambiguous.
What does “arithmetic total” mean?
The model adds the component volumes. It does not model a physical change in volume after mixing, product left in measuring containers, application losses or usable coverage. The output is a component-volume plan, not a prediction of a coating’s final performance or yield.
For a purchasing estimate based on area and coverage, use the paint planner. To compare quoted tins using their individual coverage figures, use paint offer comparison. Neither requires assuming a mixing ratio from this tool.
Keep a clear record
Copy, download or print the checked result with its ratio order, starting mode and unit. The text includes both percentage interpretations so a number is not detached from its reference amount. Calculator code does not automatically store or submit your values. See Privacy for hosting, analytics and advertising details.
To report an arithmetic issue, email coatcount.visa722@aleeas.com with your starting mode, unit, amount and both ratio parts. Open the mix ratio calculator →