How to use the resin ratio calculator
- Check your kit: is the ratio given by volume or by weight? It is on the bottle or the technical data sheet.
- Enter the ratio, for example 1 and 1, 2 and 1, or 100 and 45.
- Choose whether you know the total you need, or the amount of Part A or Part B you have left.
- Enter the amount. Results update instantly in mL, fl oz, cups, grams or ounces.
The ratio formula
Total parts = A + B Part A = Total × A ÷ (A + B) Part B = Total × B ÷ (A + B) If you know Part A: Part B = Part A × B ÷ A
Worked examples
- 2 : 1 by volume, 300 mL total: 300 ÷ 3 = 100 → 200 mL resin + 100 mL hardener.
- 100 : 45 by weight, 290 g total: 290 ÷ 145 = 2 → 200 g resin + 90 g hardener.
- Only 150 g of resin left at 100 : 45: 150 × 45 ÷ 100 = 67.5 g hardener, 217.5 g total.
Common epoxy ratios
| Ratio | Part A share | Part B share | Typical products |
|---|---|---|---|
| 1 : 1 (volume) | 50% | 50% | Art resin, tabletop coating |
| 2 : 1 (volume) | 66.7% | 33.3% | Deep-pour and casting resin |
| 3 : 1 (volume) | 75% | 25% | Deep-pour river table resin |
| 4 : 1 (volume) | 80% | 20% | Laminating and some marine epoxies |
| 5 : 1 (volume) | 83.3% | 16.7% | Marine and boat-building epoxy |
| 100 : 45 (weight) | 69% | 31% | Casting resins sold by weight |
Converting a volume ratio to weight
If your kit gives a volume ratio but you prefer to weigh (it is more accurate for small batches), you need the density of each part from the technical data sheet. Multiply each part of the ratio by its density. For example, a 2 : 1 volume ratio with resin at 1.15 g/mL and hardener at 0.95 g/mL becomes 2.30 : 0.95 by weight, which is 100 : 41.3. Never guess the densities — the difference between parts is often 10–20%, enough to leave a soft cure.
Mixing tips
- Mix for the time on the label (often 3–5 minutes), scraping the sides and bottom of the cup.
- Double-cup for clear coats: mix, pour into a clean cup and mix again to avoid unmixed streaks from the cup walls.
- Warm the bottles in warm water if the room is cold — thick resin traps bubbles.
- Mix only what you can pour within the pot life. A big mass in a cup gets hot and cures much faster than a thin layer.
- Wear nitrile gloves and work in a ventilated room. Uncured epoxy is a skin sensitiser.