Resin Mix Ratio Calculator
Enter how much epoxy you want to mix and the ratio on your label. The calculator tells you exactly how much Part A (resin) and Part B (hardener) to measure, by volume or by weight.
Measure
| Part A (resin) | – |
| Part B (hardener) | – |
| Total mixed | – |
Next steps
Not sure how much to mix? Calculate it from your mold sizeConvert ounces, ml and gramsSee how the calculation worksHow to use this calculator
- Enter the ratio from your resin label, for example 1:1 or 2:1. Tap a common ratio above to fill it in.
- Choose whether your label measures by volume (cups) or by weight (scale).
- Enter the total you want to mix, or the amount of Part A you already poured.
- Measure Part A and Part B exactly, then mix slowly for about 3 minutes, scraping the sides and bottom.
How the calculation works
For a ratio of A:B, the total is split into A + B equal shares:
- Part A = total × A ÷ (A + B)
- Part B = total × B ÷ (A + B)
If you already poured Part A, the hardener you need is Part A × B ÷ A. For example, 12 fl oz of resin at 2:1 needs 6 fl oz of hardener.
Volume or weight?
Craft and table top epoxies are usually 1:1 or 2:1 by volume, so you measure them in graduated cups. Many deep pour and professional epoxies give the ratio by weight, such as 100:45, so you measure them on a scale. The two are not interchangeable, because resin and hardener rarely weigh the same per milliliter. Always follow the basis printed on your product.
| Label says | Measure with | For 300 total |
|---|---|---|
| 1:1 by volume | Cups | 150 + 150 ml |
| 2:1 by volume | Cups | 200 + 100 ml |
| 3:1 by volume | Cups | 225 + 75 ml |
| 100:45 by weight | Scale | 206.9 + 93.1 g |
Tips for an accurate mix
- Use cups with printed lines for volume, and a scale that reads to 1 gram for weight.
- For very small batches, a syringe or a scale is more accurate than eyeballing lines on a cup.
- Pour each part into a separate cup first, then combine, so you can correct a mistake before mixing.
- Never change the ratio to speed up or slow down curing. Change the room temperature instead.
Frequently asked questions
How do I mix a 2:1 epoxy resin?
Measure two parts resin to one part hardener by volume, unless your label says by weight. For 30 fl oz of mixed epoxy that is 20 fl oz of resin and 10 fl oz of hardener.
What does a 100:45 mix ratio mean?
It is a ratio by weight: 100 grams of resin for every 45 grams of hardener. For a 200 g batch, weigh 137.9 g of resin and 62.1 g of hardener.
Can I use a volume ratio on a scale?
No. Resin and hardener usually have different densities, so 1:1 by volume is not 1:1 by weight. Use the ratio exactly as your label states it, and switch this calculator to match.
I already poured the resin. How much hardener do I add?
Choose "I know Part A" and enter what you poured. For example, 12 fl oz of resin at 2:1 needs 6 fl oz of hardener, for 18 fl oz in total.
Will extra hardener make epoxy cure faster?
No. Epoxy cures by a chemical reaction that needs the exact ratio. Extra hardener or extra resin leaves sticky, soft or bendy spots that never fully cure.