A mixing ratio describes how much of each ingredient goes into a mixture relative to the others – 2 : 1 epoxy, 50 : 1 two-stroke fuel, 1 : 3 : 6 concrete or 2 : 3 blue-to-yellow paint for a particular green. The ratio is independent of batch size, so the same recipe makes a spoonful or a drum as long as every part is scaled by the same factor.
Working with ratios means converting between three forms. Parts (2 : 3) are easiest to remember; percentages (40% and 60%) are easiest to compare; and absolute amounts (40 mL and 60 mL for a 100 mL batch) are what you actually measure. This calculator does all three at once for up to 30 components, reduces decimal recipes such as 0.5 : 1.25 to whole numbers (2 : 5), and scales the recipe either by a multiplier or to a total you choose.
Measure every component in the same unit and on the same basis – all by volume or all by mass. Mixing a volume ratio with a mass ratio is the classic source of failed resin and paint batches, because liquids have different densities.
How to use the Mixing Ratio Calculator
- Components – one per line, name and amount
- Scale the recipe by
- Multiplier
- Target total amount
- Unit (optional, for display)
Everything is calculated in your browser, so results appear instantly and nothing you type is sent to a server.
How it works
Each line is read as a name and an amount. The calculator sums the amounts, divides each by the total for its share, divides by the greatest common divisor for the simplest whole-number ratio, and multiplies every amount by the scale factor (target total ÷ recipe total, or your multiplier).
Worked example
A paint recipe calls for 2 parts blue, 3 parts yellow and 0.5 parts white, and you need 1,000 mL. The recipe totals 5.5 parts, so one part is 1,000 / 5.5 = 181.82 mL. Blue = 2 × 181.82 = 363.64 mL (36.36%), yellow = 545.45 mL (54.55%) and white = 90.91 mL (9.09%). In whole numbers the recipe is 4 : 6 : 1.
A punch recipe of 350 oz scaled to 1,000 oz uses a multiplier of 1,000 / 350 = 2.857 for every ingredient.
How to enter components
Write one component per line as a name followed by its amount, separated by a colon, an equals sign or a space – for example Resin: 2, Hardener = 1 or Water 9. Lines with only a number are named Part 1, Part 2 and so on. Decimal amounts are fine, and the unit you type is only used for display.
Formula
Share of component i = aᵢ ÷ Σa × 100% · Scaled amount = aᵢ × k, with k = target total ÷ Σa (or a multiplier you choose) · simplest ratio = aᵢ ÷ gcd(a₁, a₂, …)
Worked example
Inputs — Components – one per line, name and amount: Blue paint: 2
Yellow paint: 3
White paint: 0.5; Scale the recipe by: A target total amount; Target total amount: 1,000; Unit (optional, for display): mL.
Results — Amounts and shares = Component Recipe amount Share Scaled amount
──────────────────────────────────────────────────────
Blue paint 2 36.36 % 363.6364 mL
Yellow paint 3 54.55 % 545.4545 mL
White paint 0.5 9.09 % 90.9091 mL
Total 5.5 100 % 1,000 mL; Simplest whole-number ratio = 4 : 6 : 1; Ratio relative to the smallest component = 4 : 6 : 1; Recipe total = 5.5; Scaled total = 1,000; Scale factor = 181.818182.
Key terms
- Part
- One unit of a ratio; all parts in a recipe must use the same unit.
- Mixing ratio
- The relative amounts of the components of a mixture, written a : b : c.
- Scale factor
- The number every part is multiplied by to reach the batch size.
- Greatest common divisor
- The largest number that divides all parts exactly, used to simplify a ratio.
Frequently asked questions
How do I convert a ratio to percentages?
Divide each part by the sum of all parts and multiply by 100. For 2 : 3, the total is 5 parts, so 2/5 = 40% and 3/5 = 60%.
How do I scale a mixing ratio to a batch size?
Divide the batch size by the total number of parts to get one part, then multiply. For 1,000 mL of a 2 : 3 mix, one part is 200 mL: 400 mL and 600 mL.
What does a 50 : 1 fuel mix mean?
50 parts petrol to 1 part two-stroke oil. For 5 L of petrol you add 5 / 50 = 0.1 L (100 mL) of oil.
How do I mix a 1 : 1 ratio?
Use equal amounts of both components – each is 50% of the mixture – measured in the same unit and on the same basis.
How do I simplify a ratio with decimals?
Multiply all parts by the same power of ten and divide by their greatest common divisor. 2 : 3 : 0.5 becomes 20 : 30 : 5, then 4 : 6 : 1.
Should I mix by volume or by weight?
Follow the product instructions – epoxies and paints often list both, and they differ because densities differ. Never mix a volume ratio using a scale.
Is a mixing ratio the same as a dilution ratio?
A dilution ratio is a two-component mixing ratio where one component is the diluent (usually water). For dilutions in the lab, see the dilution factor calculator.