Volume of mould (cm³ = ml), then add waste. Split by mix ratio to get Part A and Part B. For example, a 20×15×2cm slab = 600ml volume. With 10% waste = 660ml. At 2:1 ratio: Part A = 440ml, Part B = 220ml.
Calculate the volume of your mould in cm³ (same as ml). For a rectangle: L × W × Depth. Add 10% for mixing waste. Then split by mix ratio — for a 2:1 ratio with 660ml total, you need 440ml Part A and 220ml Part B.
2:1 means 2 parts resin (Part A) to 1 part hardener (Part B). This can be by volume or by weight — always check your brand's datasheet. Getting the ratio wrong means the resin won't cure properly and will stay tacky or remain soft permanently.
Most epoxy resins weigh approximately 1.1–1.2g per ml, so 1 litre of mixed resin weighs about 1,100–1,200 grams. Check the specific gravity (SG) on your resin's technical datasheet for precision, especially for river table or thick-pour projects.
Always add at least 10% extra to your calculated volume for mixing losses and material sticking to your cup. For large or deep pours, add 15–20% buffer. It's better to have 100ml left over than run 50ml short mid-project. Round up to the nearest available bottle size.
Sticky resin is almost always an incorrect mix ratio or insufficient mixing. Measure accurately (use a scale if the ratio is by weight), scrape the sides and bottom of your cup, and stir for the full 3–5 minutes. Temperature matters too — curing stalls below 18°C and may fail entirely below 10°C.