Epoxy mix ratio by volume and by weight: why they differ
A mix ratio says how many parts of resin (part A) go with how many parts of hardener (part B). To split a batch, add the parts: with a 2:1 ratio there are 3 parts, so the resin is 2/3 of the batch and the hardener 1/3. A 32 fl oz batch at 2:1 is 21.33 fl oz of resin and 10.67 fl oz of hardener.
The label also says whether the ratio is by volume or by weight, and the two are not interchangeable. Resin and hardener have different densities, so two cups of resin do not weigh twice as much as one cup of hardener. Putting a by-volume ratio straight onto a scale gives the wrong mix.
To convert, multiply each part by its density: weight of A = volume parts of A × density of A, and the same for B. Example from a published data sheet: a deep pour epoxy mixed 2:1 by volume, with a resin of 9.3 lb per US gallon and a hardener of 8.0 lb per US gallon. By weight that is 2 × 9.3 = 18.6 to 1 × 8.0 = 8.0, or 100 parts of resin to 43 parts of hardener, which is the by-weight ratio the same sheet prints. Going the other way, divide each weight part by its density.
The epoxy mix ratio calculator splits a batch in either direction and, when you enter the two densities, shows both ratios side by side. Once you know the amounts, the epoxy resin cost calculator tells you how many kits that is.
Limits: densities differ from product to product and are printed on the technical data sheet, usually as pounds per gallon or as specific gravity. The densities this site starts with belong to one product and are only an example; use your own product's figures, and follow its label where it gives a by-weight ratio directly.
Mix chart by volume: resin and hardener for a batch (US fluid ounces), by parts of resin to 1 part of hardener
Down the side is the total batch in US fluid ounces; across the top is the number of parts of resin to one part of hardener, so the column 2 is a 2:1 kit. Measured in cups, by volume.
| Ratio: parts of resin (A) | ||||
|---|---|---|---|---|
| Amount, by volume | 1 | 2 | 3 | 4 |
| 8 US fl oz | 4.00 US fl oz resin (A), 4.00 US fl oz hardener (B) | 5.33 US fl oz resin (A), 2.67 US fl oz hardener (B) | 6.00 US fl oz resin (A), 2.00 US fl oz hardener (B) | 6.40 US fl oz resin (A), 1.60 US fl oz hardener (B) |
| 16 US fl oz | 8.00 US fl oz resin (A), 8.00 US fl oz hardener (B) | 10.67 US fl oz resin (A), 5.33 US fl oz hardener (B) | 12.00 US fl oz resin (A), 4.00 US fl oz hardener (B) | 12.80 US fl oz resin (A), 3.20 US fl oz hardener (B) |
| 32 US fl oz | 16.00 US fl oz resin (A), 16.00 US fl oz hardener (B) | 21.33 US fl oz resin (A), 10.67 US fl oz hardener (B) | 24.00 US fl oz resin (A), 8.00 US fl oz hardener (B) | 25.60 US fl oz resin (A), 6.40 US fl oz hardener (B) |
| 64 US fl oz | 32.00 US fl oz resin (A), 32.00 US fl oz hardener (B) | 42.67 US fl oz resin (A), 21.33 US fl oz hardener (B) | 48.00 US fl oz resin (A), 16.00 US fl oz hardener (B) | 51.20 US fl oz resin (A), 12.80 US fl oz hardener (B) |
| 128 US fl oz | 64.00 US fl oz resin (A), 64.00 US fl oz hardener (B) | 85.33 US fl oz resin (A), 42.67 US fl oz hardener (B) | 96.00 US fl oz resin (A), 32.00 US fl oz hardener (B) | 102.40 US fl oz resin (A), 25.60 US fl oz hardener (B) |
Mix chart on a scale: a 2:1 by volume kit weighed out, by batch weight (grams) and hardener density (lb per US gallon)
A kit labelled 2:1 by volume, resin at 9.3 lb per US gallon, weighed on a scale. Each column is a different hardener density: the lighter the hardener, the smaller its share by weight. Read your own densities from the data sheet.
| Density of the hardener (B) | ||||
|---|---|---|---|---|
| Amount, by weight | 8 lb/US gal | 8.2 lb/US gal | 8.5 lb/US gal | 9 lb/US gal |
| 100 g | 69.9 g resin (A), 30.1 g hardener (B) | 69.4 g resin (A), 30.6 g hardener (B) | 68.6 g resin (A), 31.4 g hardener (B) | 67.4 g resin (A), 32.6 g hardener (B) |
| 250 g | 174.8 g resin (A), 75.2 g hardener (B) | 173.5 g resin (A), 76.5 g hardener (B) | 171.6 g resin (A), 78.4 g hardener (B) | 168.5 g resin (A), 81.5 g hardener (B) |
| 500 g | 349.6 g resin (A), 150.4 g hardener (B) | 347.0 g resin (A), 153.0 g hardener (B) | 343.2 g resin (A), 156.8 g hardener (B) | 337.0 g resin (A), 163.0 g hardener (B) |
| 1,000 g | 699.2 g resin (A), 300.8 g hardener (B) | 694.0 g resin (A), 306.0 g hardener (B) | 686.3 g resin (A), 313.7 g hardener (B) | 673.9 g resin (A), 326.1 g hardener (B) |
| 2,000 g | 1,398.5 g resin (A), 601.5 g hardener (B) | 1,388.1 g resin (A), 611.9 g hardener (B) | 1,372.7 g resin (A), 627.3 g hardener (B) | 1,347.8 g resin (A), 652.2 g hardener (B) |
Used by
- Epoxy mix ratio calculatorEnter the mix ratio from the label, by volume or by weight, and the amount you need. You get the resin and hardener amounts, in volume and in weight.