Mixing Ratio Calculator
The amounts for a two-part mix at a given ratio — resin and hardener, fuel and oil, concentrate and water.
A ratio like 4:1 means four parts of A to one of B, so five parts total.
How the mixing ratio calculator works
A ratio like 4:1 means four parts of A to one of B, so five parts total. For a target total, each part is total ÷ (a + b).
The common trap is ratios written as "1:50" for two-stroke fuel, which means one part oil to fifty of petrol — 51 parts total, not 50. The two readings differ by 2%, which for a resin cure can matter.
Formula: A = total × a/(a+b); B = total × b/(a+b)
Worked examples
| Inputs | Part A | Note |
|---|---|---|
| 4:1 resin, 500 mL total | 400 | 400 mL resin, 100 mL hardener |
| From 400 mL of resin | 400 | add 100 mL of hardener |
| 50:1 two-stroke fuel | 5,000 | 100 mL of oil per 5 L of petrol |
FAQFrequently asked questions
What does a 4:1 ratio mean?
Four parts of the first component to one of the second — five parts in total, so A is 80% of the mix.
Is 50:1 fuel one part in fifty or one in fifty-one?
One part oil to fifty of petrol, so fifty-one total. In practice the 2% difference does not matter for fuel; for a resin cure it can.
Should I mix by weight or volume?
Whatever the manufacturer specifies. Epoxy ratios are often given both ways and they are not the same numbers, because the two components have different densities.
What happens if I get the ratio wrong?
For epoxy, an incorrect ratio does not cure properly — excess of either component leaves a soft or brittle result. Adding extra hardener does not make it set faster.
Does mixing order matter?
For safety, sometimes very much — always add acid to water, never the reverse. For resins, mix thoroughly and scrape the sides; unmixed material at the edge will stay liquid.
Where these figures come from
- IUPAC — Standard atomic weights (2021 conventional values) — the molar-mass table
- NIST — CODATA 2018 fundamental physical constants — Avogadro constant, gas constant, speed of light
- NIST Chemistry WebBook — thermochemical data
- CSIRO — Australia's national science agency
Last checked: September 2026. Atomic masses are the IUPAC conventional values; constants are CODATA 2018; equations are the standard textbook forms.