Epoxy Mix Ratio 2:1
A 2:1 epoxy ratio means 2 parts resin to every 1 part hardener by volume. This is the standard ratio for marine epoxies, structural laminates, and many deep-pour casting systems. Resin makes up two-thirds of the batch; hardener makes up one-third.
Know your 2:1 ratio — calculate exactly how much resin and hardener your project needs.
Use the Free Calculator →What 2:1 Ratio Means
In a 2:1 mix, for every 2 units of Part A (resin) you add 1 unit of Part B (hardener). The ratio describes volume proportions — the "unit" can be fl oz, mL, cups, or any consistent measure.
Resin = Total × (2/3) = Total × 0.667
Hardener = Total × (1/3) = Total × 0.333
Example: Need 30 fl oz total
Resin = 30 × 0.667 = 20 fl oz
Hardener = 30 × 0.333 = 10 fl oz
The simpler way to think about it: the hardener is always exactly half the volume of the resin. Measure your resin first, then pour hardener to half that amount.
Quick check: Hardener = Resin ÷ 2. If you have 24 fl oz of resin, you need 12 fl oz of hardener. Total mixed = 36 fl oz.
2:1 Batch Size Reference Table
Find your total project requirement in the left column, then read across for component amounts. Remember to add 10% to your calculated need before looking up batch size.
| Total Mixed | Part A Resin (⅔) | Part B Hardener (⅓) | Total in mL |
|---|---|---|---|
| 6 fl oz | 4 fl oz | 2 fl oz | ~177 mL |
| 12 fl oz | 8 fl oz | 4 fl oz | ~355 mL |
| 18 fl oz | 12 fl oz | 6 fl oz | ~532 mL |
| 24 fl oz | 16 fl oz | 8 fl oz | ~710 mL |
| 36 fl oz | 24 fl oz | 12 fl oz | ~1,065 mL |
| 48 fl oz | 32 fl oz | 16 fl oz | ~1,420 mL |
| 72 fl oz | 48 fl oz | 24 fl oz | ~2,130 mL |
| 96 fl oz (¾ gal) | 64 fl oz | 32 fl oz | ~2,839 mL |
| 128 fl oz (1 gal) | 85.3 fl oz | 42.7 fl oz | ~3,785 mL |
Metric 2:1 Batch Sizes
| Total Mixed (mL) | Part A Resin | Part B Hardener |
|---|---|---|
| 150 mL | 100 mL | 50 mL |
| 300 mL | 200 mL | 100 mL |
| 600 mL | 400 mL | 200 mL |
| 1,000 mL (1 L) | 667 mL | 333 mL |
| 2,000 mL (2 L) | 1,333 mL | 667 mL |
| 5,000 mL (5 L) | 3,333 mL | 1,667 mL |
Products That Use 2:1 Ratio
Marine & Structural Epoxies
2:1 by volume is the dominant ratio for marine laminating epoxies, boat building, and structural repairs. The higher resin content produces good wetting of fiberglass cloth and wood.
- West System 105 Resin with 207 or 206 hardener — 5:1 by weight (check label, not volume)
- System Three General Purpose Epoxy — 2:1 by volume
- MAS Epoxies LV Slow — 2:1 by volume
- Raka Epoxy 127 — 2:1 by volume
Note: West System uses a 5:1 ratio by weight (not volume) — always verify your specific product against its technical data sheet.
Casting & Deep-Pour Resins
Some deep-pour systems use 2:1 to slow the exothermic reaction. With a higher resin volume, less hardener is present, which slows cure and reduces heat generation — important for thick pours.
- TotalBoat ThickSet Deep Pour — 2:1 by volume
- Various deep-pour casting resins — check label (may be 1:1 or 2:1)
How to Measure 2:1 Accurately
Method 1: Graduated Mixing Cup (Most Common)
- Choose a mixing cup large enough for your full batch.
- Pour resin to your desired volume mark (e.g., 20 fl oz).
- Note the resin level, then add hardener to bring the total to 1.5× the resin volume (e.g., 20 fl oz resin → add hardener to 30 fl oz total).
- Mix thoroughly for 3–5 minutes, scraping the sides and bottom.
Method 2: Two Separate Containers
- Measure the full resin amount in one container.
- Measure exactly half that volume as hardener in a second container.
- Combine both into a large mixing bucket and mix thoroughly.
Method 2 is more accurate for large batches because you avoid reading a combined scale at ⅔ increments — half is easier to measure precisely.
Never estimate the hardener. At 2:1, the hardener is only one-third of the batch — a small measuring error is a larger proportional error than with 1:1. Use calibrated cups or a digital scale if your product specifies weight ratios.
2:1 vs 1:1 Epoxy — Key Differences
| Property | 1:1 Ratio | 2:1 Ratio |
|---|---|---|
| Hardener fraction | 50% of batch | 33% of batch |
| Typical applications | Tabletop, art resin, countertop | Marine, structural, some casting |
| Measuring difficulty | Easy (halve the total) | Moderate (1/3 of total) |
| Pot time (typical) | 20–45 min | 20–60 min (varies) |
| Cure hardness (typical) | Moderate to hard | Hard to very hard |
Frequently Asked Questions
What does a 2:1 epoxy ratio mean?
Two parts resin to one part hardener by volume. Resin makes up 2/3 of the mixed batch; hardener makes up 1/3. The hardener amount always equals exactly half the resin volume.
How much hardener do I add to 32 fl oz of resin at 2:1?
16 fl oz of hardener (half the resin amount). Total mixed batch = 48 fl oz.
Is West System epoxy 2:1?
West System uses a 5:1 resin-to-hardener ratio by weight for most pumped systems. Their ratio is specified by weight, not volume, which is unusual. Always refer to the West System product data sheet for the specific hardener you're using.
Can I add a bit more hardener to make epoxy cure faster?
No. Adding more hardener than specified does not accelerate cure — it causes an incorrect ratio that leads to soft spots, cloudiness, or sticky uncured areas. Cure speed is controlled by temperature and hardener type (slow vs. fast), not by adding extra hardener.