Resin volume for mold calculator

Enter the internal length, width, and planned pour depth, then choose millimeters, centimeters, or inches. The calculator converts capacity to milliliters and liters and uses your resin system's mixed density to estimate weight. You can also account for multiple identical molds, a partial fill, and extra material left behind in cups or lost during handling.

Measure the space the resin will actually occupy

Use internal mold measurements, not the outside dimensions of the mold box. Measure the usable length and width at the level the resin will occupy, then enter the planned pour depth rather than the full wall height unless you genuinely intend to fill to the top. Keep all three measurements in the same unit and select that unit in the calculator. For a simple rectangular cavity, volume is length multiplied by width multiplied by depth. The calculator converts that result to milliliters, where one cubic centimeter equals one milliliter. If you have several identical cavities, quantity multiplies the filled volume after the single-cavity capacity is established. Flexible silicone molds can bow or have rounded corners, so their real capacity may differ slightly from a perfect rectangular model. For an irregular mold, a careful water-fill measurement is usually more accurate, provided the mold material can safely contact water and is completely dry before resin is poured. This calculator is intended for rectangular geometry and gives a transparent planning estimate rather than pretending that every handmade mold is exact.

Turn mold volume into mixed resin weight

Resin volume and resin weight are related by the density of the fully combined mixture. Enter mixed density in grams per milliliter from the resin manufacturer's technical data sheet. The default is only a practical starting value, not a universal property of epoxy, polyurethane, polyester, or acrylic casting systems. The calculator multiplies the required fill volume by density to return mixed weight in grams. This is the total mixed material, before separating that weight into Part A and Part B. Follow the product's stated mix ratio separately, and pay close attention to whether that ratio is specified by weight or by volume; those methods are not interchangeable unless the manufacturer explicitly says so. Pigments, mineral fillers, metal powders, aggregate, embedded objects, and displacement pieces can change either effective density or the amount of liquid resin that fits. For precise production work, make a small verified test pour and update the density or fill assumptions from measured results. Never infer component weights from mixed density alone, because individual component densities and the prescribed ratio determine that split.

Plan fill level, handling loss, and a safe batch

Fill percentage lets you model a pour that occupies less than the full rectangular capacity. For example, a shallow decorative layer can be represented by entering its actual depth, while fill percentage is more useful for a deliberately underfilled cavity or a repeatable allowance below the rim. Avoid reducing both depth and fill percentage for the same empty space, because that counts the reduction twice. Waste percentage adds material after the required fill volume and mixed weight have been calculated. This allowance can cover resin coating the mixing cup and stirrer, small transfer spills, syringe or pipette hold-up, and uncertainty in handmade dimensions. It is not a substitute for respecting the resin's maximum pour depth, pot life, exotherm limits, ventilation requirements, or protective-equipment instructions. Large batches can heat rapidly even when the geometry fits the mold. Review the product data sheet before mixing, divide a pour into approved layers when required, and prepare molds and inclusions before combining components. API automation costs $0.002 per request, while the same deterministic calculation can run in the browser for quick workshop planning.