Calculate epoxy resin and hardener mixing ratios.
Use 1:1, 2:1, 3:1, 4:1, 5:1, 100:45 or any custom ratio. Start from the total batch you want, the resin amount you already have, or the hardener amount you need to work from.
Calculate resin and hardener from whatever amount you know.
Start from the total batch, a known resin amount or a known hardener amount. Always use the exact ratio and weight/volume basis stated by the manufacturer.
How epoxy resin and hardener ratios work
A ratio such as 2:1 means two parts resin for every one part hardener. The total mixture therefore contains three parts. A 3:1 ratio contains four total parts, while a 1:1 ratio contains two equal parts.
Epoxy resin to hardener ratio chart
These examples show how a 1,000 g total batch is split for common resin-to-hardener ratios. Use a ratio only when the manufacturer specifies that exact ratio and measurement method.
| Mix ratio | Resin share | Hardener share | 1,000 g total batch |
|---|---|---|---|
| 1:1 | 50% | 50% | 500 g + 500 g |
| 2:1 | 66.7% | 33.3% | 666.7 g + 333.3 g |
| 3:1 | 75% | 25% | 750 g + 250 g |
| 4:1 | 80% | 20% | 800 g + 200 g |
| 5:1 | 83.3% | 16.7% | 833.3 g + 166.7 g |
| 100:45 | 69.0% | 31.0% | 689.7 g + 310.3 g |
How much hardener do I add to resin?
If you already know the resin amount, you do not need to calculate the full batch first. For a 2:1 ratio, divide the resin amount by two: 500 g of resin needs 250 g of hardener. For a 3:1 ratio, divide the resin amount by three: 600 g of resin needs 200 g of hardener. The calculator above can do this directly using the Resin input mode.
Example: 2:1 epoxy mixing ratio
For a 900 g total batch at 2:1, divide 900 by three. One part is 300 g, so the batch contains 600 g resin and 300 g hardener. If the product specifies 2:1 by volume instead, use the same part logic with the volume units stated by the manufacturer.
Example: 3:1 resin and hardener ratio
A 3:1 ratio contains four total parts. For an 800 g total batch, one part is 200 g, so the correct split is 600 g resin and 200 g hardener.
Example: 100:45 by weight
A 100:45 ratio contains 145 total parts. For a 1,000 g batch, resin is 1,000 × 100/145 ≈ 689.7 g and hardener is 1,000 × 45/145 ≈ 310.3 g.
Weight ratio vs volume ratio
They are not automatically interchangeable. Resin and hardener often have different densities, so a product listed as 2:1 by volume may use a different ratio by weight. Always choose the measurement method stated by the manufacturer. If your kit is sold by mass but your project result is in litres, use the epoxy resin density calculator.
Epoxy ratio is not the same as polyester catalyst percentage
This calculator is for two-part epoxy systems. Polyester resin is commonly dosed with a catalyst percentage rather than an epoxy-style resin-to-hardener ratio, so do not use these results for polyester catalyst calculations.
Why accurate epoxy mixing matters
Incorrect proportions can leave epoxy soft, sticky or incompletely cured. Measure carefully, scrape the container sides and bottom while mixing, and follow the product's published mixing time, temperature and batch-size limits.