About this tool
Epoxy Resin Volume Calculator is a free, in-browser tool that tells you how much resin to mix for a mold, coaster, tabletop coating or round cast. Choose a rectangular or round shape, enter the dimensions in inches, centimeters or millimeters, and it returns the total mixed volume, the Part A and Part B split for your ratio, the volume in fluid ounces and the total weight. Everything is computed locally; nothing is uploaded.
The method finds the geometric volume — length × width × thickness for a rectangle, or π × radius² × thickness for a round pour — after converting every dimension to centimeters, so 1 cm³ equals 1 ml directly (inches are handled internally as 1 in³ ≈ 16.387 ml). It then adds a waste buffer (10% by default) for the resin left clinging to the mixing cup and stir stick. Part A and Part B come from your mix ratio: for a 2:1 resin, Part A = total × 2⁄3 and Part B = total × 1⁄3. Weight = total volume × density, using about 1.1 g/ml for typical epoxy.
Use the buffer to avoid mixing a second batch mid-pour, which risks visible layers. Always follow your resin's exact mix ratio by the method it specifies — most casting and coating epoxies are ratioed by volume, which is what this tool splits.