Resin Pour Calculator

Epoxy resin volume for flat work: how much mixed resin (Part A plus Part B) it takes to coat a surface, fill a tray, or run a river table channel. Resin is sold and mixed by volume or by weight depending on the product.

Volume = Length × Width × Depth. In centimetres that lands in millilitres directly, because 1 cm³ and 1 mL are the same thing.

This page is rectangular on purpose, because flat work almost always is. For a shaped mold, a sphere, dome, cylinder, cone or pyramid, the resin casting calculator carries the geometry for each one. The depth advice below still applies there.

Mix ratio formula (by volume): Most epoxy resins use 1:1 or 2:1 (A:B) by volume ratios.

For 2:1 ratio (2 parts resin : 1 part hardener):

• Part A (resin) = Total Volume × (2 ÷ 3)
• Part B (hardener) = Total Volume × (1 ÷ 3)

Overage factor: Always add 10–15% overage, because resin is lost to the container walls, the mixing stick, and spills. Shallow pours may need 20% extra for surface leveling.

Weight from volume: Weight (g) = Volume (mL) × Specific Gravity Typical epoxy specific gravity: 1.1–1.2 g/mL

What each variable means:

• Depth of pour: this is the one that catches people out, and the two product families work in opposite directions. Art and coating resins cure fast and generate a lot of heat, so they cap out around ¼ inch (6 mm) per layer. Deep-pour casting resins are formulated to cure slowly for exactly this reason and will take 1 to 2 inches in a single pour, some more. Using a coating resin for a deep pour is what cracks and yellows a piece.
• Exothermic reaction: mixing resin generates heat. Deep pours in confined molds can crack, yellow, or even catch fire if maximum pour depth is exceeded.
• Cure time vs hardener type: slow hardeners (24–72 hr) allow bubbles to escape; fast hardeners (2–4 hr) trap bubbles but work faster.

Reference: resin volumes for common projects

• Coaster (4 in round, ¼ in deep): ~50 mL
• Small tray (8 in × 12 in × ¼ in): ~390 mL
• River table channel (6 ft long, 6 in wide, 1 in deep): ~7,100 mL, so 7 litres
• Tumbler coating (1 layer): ~30–60 mL

Those first two are worth checking against your own instinct, because most people guess high. A 4-inch coaster holds about three tablespoons of resin.

Worked example: Rectangular mold: 20 cm × 30 cm × 2 cm deep. Using 2:1 ratio epoxy.

Total volume = 20 × 30 × 2 = 1,200 mL With 12% overage = 1,200 × 1.12 = 1,344 mL total needed

Part A = 1,344 × 2/3 = 896 mL resin Part B = 1,344 × 1/3 = 448 mL hardener

Weight = 1,344 mL × 1.15 g/mL = 1,545.6 g ≈ 1.55 kg of mixed resin