2:1 epoxy ratio: how much of each part by weight?
A 2:1-by-volume epoxy is about 100 : 42 by weight at typical densities (resin SG 1.15, hardener 0.97 — typical, not published by any maker), so a 16 fl oz batch is 12.8 ounces of Part A and 5.4 ounces of Part B on a scale. By volume that’s 10.7 fluid ounces and 5.33 fluid ounces.
How to work it out
- 2 : 1 by volume → by weight 2 × 1.15 : 1 × 0.97 = 100 : 42 (SGs typical, not published by the maker)
- Batch 16 fl oz (18.2 oz) → A 12.8 oz (10.7 fl oz) + B 5.4 oz (5.33 fl oz)
Many deep-pour casting resins and laminating epoxies mix 2:1 by volume — MAS Deep Pour X and EcoPoxy FlowCast are two. Because the hardener is usually lighter than the resin, the weight ratio drifts further from 2:1 than you might expect, and measuring 2:1 by weight would leave you short of hardener relative to what the chemistry needs. If your product’s data sheet lists its own weight ratio, use that instead of these typical densities — FlowCast’s, for example, is 2.3 : 1.
Adjust for your project
- Part A by weight
- 12.8 oz (363 g)
- Part B by weight
- 5.4 oz (153 g)
- Part A by volume
- 10.7 fl oz (315 ml)
- Part B by volume
- 5.33 fl oz (158 ml)
- Ratio by weight
- 100 : 42 (2.37 : 1)
- Ratio by volume
- 100 : 50 (2 : 1)
- Total batch weight
- 18.2 oz (516 g)
- Total batch volume
- 16 fl oz (473 ml)
- The weights use SGs of 1.15 (A) and 0.97 (B) — typical, not published by the maker, since the boxes are blank. Type your data sheet’s figures for exact weights.
- Specific gravities vary by product. Use the values on your epoxy’s technical data sheet — or the weight ratio it lists, which is the most reliable figure.
A 16 fl oz batch of 2:1 epoxy: weights by hardener density
| Part B specific gravity | Part A by weight | Part B by weight | Ratio by weight |
|---|---|---|---|
| Hardener SG 0.9 | 12.8 oz | 5.01 oz | 100 : 39 (2.56 : 1) |
| Hardener SG 0.95 | 12.8 oz | 5.29 oz | 100 : 41 (2.42 : 1) |
| Hardener SG 0.97 | 12.8 oz | 5.4 oz | 100 : 42 (2.37 : 1) |
| Hardener SG 1 | 12.8 oz | 5.56 oz | 100 : 43 (2.3 : 1) |
| Hardener SG 1.05 | 12.8 oz | 5.84 oz | 100 : 46 (2.19 : 1) |
| Hardener SG 1.1 | 12.8 oz | 6.12 oz | 100 : 48 (2.09 : 1) |
What to know about weighing a 2:1 epoxy
- The hardener is the small number, so it carries the error. In a 2:1 system Part B is only a third of the batch. On a small pour — a few fluid ounces for a knot, a crack or a test cup — that’s a fraction of an ounce, and a scale that reads in whole grams is far more precise than the lines on a cup. Switch your scale to grams for anything under a pint; the calculator shows grams next to ounces.
- Weighing 2:1 by weight is the classic mistake. If the label says 2:1 by volume and you put 2 parts resin to 1 part hardener on the scale, the hardener’s lower density means you actually pour about a fifth more hardener by volume than the resin expects — roughly 1.69 : 1 instead of 2 : 1. The result can stay soft or tacky and won’t improve with time.
- Real 2:1 products publish their own numbers. Pick EcoPoxy FlowCast in the product list and the calculator uses its data-sheet densities (1.122 and 0.978), which give 2.29 : 1 by weight rather than the 2.37 : 1 of these typical figures. MAS Deep Pour X gives no weight ratio on its product page, so check the data sheet that ships with the kit.
- Big deep pours are easier by volume — with the right buckets. A 1.5-gallon kit mixed in one go is too heavy for most kitchen scales; graduated buckets marked for 2:1, or pouring each jug out in full, keep you on ratio. Check whether the kit size on the box is the combined A + B volume before you plan batches — the epoxy cost calculator handles kits named by Part A only.
Most art and tabletop resins are 1:1 instead — the same logic in grams is worked through in 1:1 epoxy by weight in grams. To turn a whole batch or a kit into pounds, see how much a gallon of epoxy weighs.
Different size? Use the full Epoxy Mix Ratio Calculator.
What you’ll need
- Digital scale (0.1 g)Budget price
For mixing by weight. Far more accurate than cup lines for small batches — and it doubles for the water method on molds.
See options on Amazon (opens in a new tab) - Graduated mixing bucketsBudget price
Marked buckets make accurate Part A / Part B ratios easy — mismeasured ratios are a leading cause of soft, sticky cures.
See options on Amazon (opens in a new tab) - Graduated mixing cups & stir sticksBudget price
Small cups marked in ounces and ml for art, coasters and tumblers. Use a fresh cup when you transfer to a second container.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How much Part A and Part B for a 32 oz batch of 2:1 epoxy by weight?
About 25.6 ounces of resin and 10.8 ounces of hardener — 36.4 oz in all for 32 fluid ounces.
How much hardener by weight for a 2 oz batch of 2:1 epoxy?
Only about 0.67 ounces of Part B with 1.6 ounces of Part A. Weigh it in grams — at this size a couple of grams either way is a big share of the hardener.
What is a 2:1 epoxy by weight if the hardener’s specific gravity is 1.0?
About 100 : 43 — a 16 fl oz batch is 12.8 ounces of resin and 5.56 ounces of hardener.
How much does a 16 fl oz batch of EcoPoxy FlowCast weigh out to?
About 12.5 ounces of Part A and 5.44 ounces of Part B, using the data sheet’s specific gravities — 2.29 : 1 by weight, close to the 2.3 : 1 EcoPoxy lists.
I poured 8 oz of 2:1 resin by weight — how much hardener do I add?
About 3.37 ounces of Part B by weight (3.33 fl oz by volume) at typical densities, for 10 fl oz of mixed epoxy.
Other common sizes
- 1:1 epoxy by weight in grams — 288 g Part A + 238 g Part B
Sources
- MAS Epoxies — Deep Pour X product page (opens in a new tab) — 2:1 mix; poured 2–3 in thick per pour (2 in minimum — thinner pours cure slowly); about 12 h working time and a 36 h cure; 1.5, 3 and 6 gallon kits; keep materials and shop at 60–80°F; seal-coat bare wood first. No specific gravities or weight ratio listed.
- EcoPoxy — FlowCast product page (opens in a new tab) — 2:1 by volume, 2.3:1 by mass; 13–38 mm (0.5–1.5 in) per layer for pours up to 30 L; pour the next layer while the last is tacky; demold after 3 days; 6, 12, 30 and 60 L kits.
- EcoPoxy — FlowCast technical data sheet (PDF, June 2022) (opens in a new tab) — Specific gravity Part A 1.122, Part B 0.978 at 22°C; tacky-to-touch (next-layer window) 20–44 h and demold 3 days for a 72 × 8 × 1.5 in casting at 21°C.
- TotalBoat — TableTop Epoxy product page (opens in a new tab) — 1:1 by volume, 1.2:1 by weight; up to 1/4 in per coat; 2 qt, 1, 2 and 4 gal kits (A + B together); 40 min working time and at least 3 h before recoating at 70°F; full cure 5–7 days.
- WEST SYSTEM — 105 Resin / 205 Fast Hardener technical data sheet (PDF) (opens in a new tab) — 5 parts resin : 1 part hardener by volume = 5.19 : 1 by weight (acceptable 4.83–6.20 : 1); pot life 9–12 min (100 g at 72°F); cured SG 1.18.
- Epoxyworks (WEST SYSTEM): The Basics of WEST SYSTEM Epoxy Resin and Hardener (opens in a new tab) — Altering the amount of hardener does not change cure speed; it leaves a mixture that can never fully cure