Compound Mixture Ratio Calculator

What this calculator does

It performs the three ratio operations of practical mixing, for up to four components, keeping the two dialects of ratio strictly separate. A part-to-part ratio (2:1) describes components against each other; a part-to-total statement (50%) describes one component against the whole. Confusing them is the classic mixing error, doubling or halving a component, so every result on this page shows both: each component’s amount and its percentage of the total, the part-to-total audit beside the split. Mode 1 divides a total by the sum of parts. Mode 2 runs the same relation backwards from a single known component, which is the real-world case (a half-used tin of one part, a measuring jug that fits only so much). Mode 3 reduces a set of actual amounts to their simplest ratio and percentages, answering “what did I actually mix?” for a batch already made or a recipe being reverse-engineered.

How to use it

• The ratio comes from the source, in the source’s own terms. Labels state ratios by volume or by weight, and they are not interchangeable for materials of different density. Enter the ratio as given and measure your amounts in the same basis (all volumes or all weights); the calculator cannot detect a basis mix-up, and it is the most consequential error in mixing.
• Parts need not be whole, small or equal. 100:2.5, 1:0.05 and 7:3 all work. What matters is the proportion; the page scales it to your total. Ratios copied from a label should be entered exactly as printed, decimals included, because rounding a catalyst’s 2.5 to 3 is a 20% overdose delivered by arithmetic.
• Zero parts are how components retire. A two-component mix on a four-component page is parts 0 in the last fields. Zero in Mode 3 likewise means “not in this mix”, and the audit ignores it. A component that should be present but reads zero in an audit is a finding, not a bug.
• Weigh small components. When a split returns a few grams or millilitres of one part, a scale beats a jug by an order of accuracy, and ratio errors concentrate in the smallest component. The percentages in the results double as a sanity check: a hardener at 2% that your split prints as 20% has caught a misplaced decimal before the mix did.
• Audit before you repeat. Mode 3’s purpose is the second batch: a mix that worked can be recorded as its reduced ratio, and a mix that failed can be compared against the intended one in the same terms. Memory rounds; the audit does not.

How it is calculated

• Split: with parts p1…pn and total T, the sum S = p1 + … + pn; each component = T x pi / S. Its part-to-total percentage = 100 x pi / S.
• Scale from component k: the total is T = known amount x S / pk, and every other component follows from the split formula. The known component’s ratio part must be nonzero; asking to scale from a zero part is refused with the reason stated.
• Audit: amounts are divided by the smallest nonzero amount to give a ratio with smallest part 1 (shown to two decimals); where the amounts are whole numbers sharing a common factor, the reduction lands on whole parts. Percentages are each amount over the total of the amounts.

Worked examples

A two-part mix at 800 ml. Ratio 2:1 at a total of 800 ml: one part is 800 / 3 = 266.67 ml, so the split is 533.33 ml of the first component and 266.67 ml of the second, percentages 66.67% and 33.33%. Add a third part, ratio 2:1:1 across resin, hardener and filler at the same 800 ml total, and one part is 200 ml: 400.00, 200.00 and 200.00 ml, percentages 50%, 25%, 25%.

Scaling from what is left. A 3:2 mix where 150 g of the first component is what remains in the tin: the batch scales to a total of 250.00 g, the second component at 100.00 g. The alternative, guessing the second component and discarding the surplus of the first, is how workable material becomes waste.

Auditing a made mix. Amounts of 500, 250 and 125 reduce to 4 : 2 : 1, percentages 57.14%, 28.57% and 14.29%. If the intended ratio was 2:1:1 (which would be 50/25/25), the audit has caught a double measure of the first component, which is precisely the conversation Mode 3 exists to start.

Reading your results

Read amounts beside their percentages every time: the amount is what you measure, the percentage is how you catch a misplaced decimal or a part entered in the wrong field. In Mode 2, read the total first, because scaling from a component can produce a batch larger than your container, and it is better to learn that from the results than from the bench. In Mode 3, read the reduced ratio against the intended one with the tolerance of your measuring tools in mind: a ratio of 4.1:2:1 from jugs is 4:2:1 wearing measurement noise; from a scale, it is a real discrepancy.

Limitations

• Ratio correctness is entirely yours. The page computes flawlessly for a wrong ratio exactly as for a right one. Product labels, data sheets and tested recipes are the authorities; a ratio remembered from a forum post is a hypothesis, and for anything hazardous the label’s instructions, including its safety directions, govern absolutely.
• No volume-to-weight conversion. A ratio by weight cannot be measured out by volume without each material’s density, and densities are product-specific. This page deliberately offers no conversion rather than a guessed one; if your ratio is by weight, weigh; if by volume, measure.
• Rounding at small scales is real. A 1,000 ml batch at 100:1 splits to 9.90 ml of the second part, measurable; a 50 ml batch wants 0.50 ml, at the edge of home measurement. The results print two decimals faithfully and leave the practical conclusion to you: scale the batch up to a measurable size and store the surplus if the material allows.
• Four components is the page’s ceiling. Most practical mixtures are two or three parts. Recipes with more (some coating and composite systems) can be split in two passes against a subtotal, or belong in the maker’s own formulation software.

Frequently asked questions

How do I split a total by a ratio?

Add the parts to get their sum, divide the total by that sum to get one part’s size, and multiply each component’s parts by it. At 2:1:1 with a total of 800 ml, one part is 800 / 4 = 200 ml, and the components are 400, 200 and 200. Mode 1 does exactly this and prints each component’s percentage of the whole beside its amount, because the percentage is the fastest check that the split is the ratio you meant.

What is the difference between part-to-part and part-to-total?

Part-to-part compares components with each other: 2:1 means twice as much of the first as the second. Part-to-total compares one component with the finished whole: in that same 2:1 mix the first component is 66.67% of the total, not “2 of 2”. Instructions that swap dialects mid-sentence (“add 1 part hardener to 10% resin”) are the source of most mixing failures; this page’s results always show both dialects together so either instruction can be followed without translation errors.

Can I scale a recipe up or down with this?

Yes, in either direction and from either anchor: Mode 1 from the total you want, Mode 2 from the component you have. Scaling is the ratio’s home ground, since a ratio is a proportion, not a quantity. The cautions are practical rather than mathematical: very small batches push minor components below measurable amounts, and some processes (curing, cooking times, exothermic mixes) do not scale their behaviour with their quantities even though their proportions do.

Why does the calculator not suggest a ratio for my product?

Because the right ratio is a fact about your product, set by its maker and printed on its label or data sheet, and a calculator that guessed ratios for resins, fuels, chemicals or medicines would be a hazard wearing a helpful face. What the page guarantees is the arithmetic: given the ratio from the authoritative source, the amounts at any scale are exact, auditable and repeatable, which is the part of mixing a calculator can legitimately own.

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Method: part-to-total splitting by the sum of parts, inverse scaling from a single component, and audit reduction to a smallest-part-of-1 ratio with percentages, exactly as defined on this page. Ratios are user-supplied; the manufacturer or recipe source remains the authority for any specific product. Last reviewed: 13 October 2026.