How To Calculate Epoxy Resin Amounts For Any Mold
Calculating exactly how much epoxy you need to fill a mold is arguably the most stressful part of the resin-pouring process. Whether you're pouring a tabletop river desk or a small coaster, measuring accurately is key. Resin is expensive. If you mix too much, you waste money and throw away curing plastic. If you mix too little, you run the massive risk of missing your open working time (pot life) while scrambling to mix a second batch. Our resin volume calculator prevents these expensive mistakes.
The "Cubic Inches" Epoxy Coverage Formula
Our Epoxy Calculator determines your mixed total by finding the volume of your mold in cubic inches, acting as the perfect deep pour calculator or tabletop epoxy calculator.
For a Rectangle or Square (e.g., cutting boards, table tops): Multiply Length × Width × Height (Pour Depth).
For a Circle (e.g., round coasters, clock faces): Multiply π (approx 3.14159) × Radius squared × Height.
Once you have the total cubic inches, simply divide that number by 1.805. One fluid ounce contains exactly 1.805 cubic inches of space. The result is the exact number of fluid ounces required to fill your designated space. We automatically add a 5% "mixing waste buffer" to our results, because resin will adhere to the walls of your silicone mixing cups and wooden stirring sticks, reducing your net pour volume.
Volume vs Weight: A Critical Epoxy Resin Warning
Many beginners attempt to measure a standard 1:1 tabletop epoxy by setting a cup on a digital scale and pouring equal weights of Part A and Part B. Do not do this unless your resin instructions specifically tell you to mix by weight!
Most hobbyist 1:1 and 2:1 epoxies are formulated by Volume. Part A (the resin) shrinks differently chemically and is significantly denser and heavier than Part B (the hardener). If you use a scale to measure a volume-based resin by weight, you will end up adding nearly 15% too much Part B, severely throwing off the stoichiometric chemical reaction. This results in a sticky, tacky, or cloudy cure that will never fully harden. Always use graduated measuring cups.
Resin Mix Ratios: Tabletop Coating vs. Deep Pour
- 1:1 Resins: Typically "Tabletop" or coating epoxies. They cure fast in thin layers (usually 1/8 to 1/4 inch deep). Great for canvases, tumblers, and sealing wood surfaces. This is the most common ratio for tabletop epoxy calculators.
- 2:1 and 3:1 Resins: Usually considered "Deep Pour" or casting epoxies. They cure very slowly (often taking 3 to 7 days) to limit intense heat generation (exothermic reaction). Excellent for river tables, deep molds, and large sphere castings.