Resin Mixing Ratio Calculator
Work out exact resin and hardener amounts for any mix ratio, by volume or weight, with pigment loading and a mould-volume helper.
Enter an amount — the resin and hardener quantities update as you type.
- Resin (part A)
- —
- Hardener (part B)
- —
- Total mixed
- —
- Pigment to add
- —
- Share of the mix
- —
- Ratio used
- —
Most pigment makers cap loading at about 6% of the mixed resin — more than that can stop the epoxy curing properly.
Is your ratio by volume or by weight?
A 2 : 1 ratio by volume is not the same as 2 : 1 by weight, because resin and hardener have different densities. Enter the densities from your product data sheet to see the equivalent ratio in the other unit.
—
How much mixed resin does my mould need?
Mould volume: — · with 10% spare: —
Always follow the mixing ratio printed on your resin's technical data sheet — ratios differ between brands and even between fast and slow hardeners in the same range. Mix thoroughly, scraping the sides and bottom of the cup, and respect the manufacturer's maximum pour depth.
How it works
Resin mixing ratios are written resin : hardener. To split a target batch the
calculator uses resin = total × R ÷ (R + H) and
hardener = total × H ÷ (R + H), so 300 ml of a 2 : 1 mix is 200 ml of resin and
100 ml of hardener. If instead you know how much of one component you have, it scales the
other: hardener = resin × H ÷ R. With a 100 : 45 epoxy, 500 g of resin needs
500 × 45 ÷ 100 = 225 g of hardener, for 725 g of mixed resin.
The ratio conversion box handles the mistake that ruins most pours: mixing a ratio given by weight using measuring cups, or the other way round. Dividing each part by its density turns a weight ratio into a volume ratio (and multiplying does the reverse), so 100 : 45 by weight at 1.15 and 0.98 g/ml becomes about 1.89 : 1 by volume. The mould helper multiplies length × width × depth to give the volume in millilitres — 1 cm³ is exactly 1 ml — and adds 10% spare for the resin that clings to the mixing cup.
Everything is plain arithmetic running in your browser: nothing you type is uploaded, stored or sent anywhere, and there are no ads or sign-ups.
Frequently asked questions
How do I calculate the resin to hardener ratio?
Ratios are written resin : hardener, so split your target batch with resin = total × R ÷ (R + H) and hardener = total × H ÷ (R + H). For a 2 : 1 epoxy and a 300 ml pour that is 300 × 2 ÷ 3 = 200 ml of resin and 300 × 1 ÷ 3 = 100 ml of hardener. If you instead know how much of one part you have, scale the other: hardener = resin × H ÷ R, so 500 g of a 100 : 45 epoxy needs 500 × 45 ÷ 100 = 225 g of hardener and gives 725 g of mixed resin.
Is a resin ratio by volume the same as by weight?
No, and mixing them up is the most common reason a pour stays tacky. Resin is usually denser than its hardener — around 1.1 to 1.16 g/ml against 0.95 to 1.0 g/ml — so the same numbers mean different quantities. Divide each side of a weight ratio by its density to get the volume ratio: 100 : 45 by weight at 1.15 and 0.98 g/ml works out to about 1.89 : 1 by volume. This calculator does that conversion for you once you type in the densities from the technical data sheet.
How much pigment can I add to epoxy resin?
Most pigment and mica makers cap loading at about 6% of the total mixed resin, and many recommend staying nearer 3–5%. Beyond that the pigment starts to interfere with the cure and you get soft or sticky patches. Enter a percentage and the calculator shows the pigment amount alongside the resin and hardener, and flags anything over 6%. Always follow the ratio, pigment limit and maximum pour depth on your own product's data sheet.