How much resin for molds?
Measure the space the resin will fill, then multiply by the number of pieces. A tray’s outside dimensions are not its cavity dimensions.
Rectangular molds
Inside length × inside width × fill depth gives the cavity volume. In centimetres, the result is cubic centimetres; 1 cm³ equals 1 mL.
10 × 10 × 1 cm = 100 mL
Four identical cavities need 400 mL before any extra material allowance. Measure the intended fill depth, rather than the mold’s full outside height.
Round molds
For a cylindrical cavity, volume = π × (inside diameter ÷ 2)² × fill depth. Enter the diameter across the cavity, not the radius.
A 10 cm diameter cavity filled 1 cm deep holds about 78.54 mL. Eight identical cavities hold about 628.32 mL.
A mixed batch: eight coasters and four trays
| Mold | Pieces | Base volume |
|---|---|---|
| Round, 10 cm diameter × 1 cm deep | 8 | 628.32 mL |
| Rectangle, 10 × 10 × 1 cm | 4 | 400 mL |
| Combined | 12 | 1,028.32 mL |
With a user-selected 10% extra allowance, that becomes about 1,131.15 mL. At a product-specified 2:1 ratio by volume, that splits into about 754.10 mL of Part A and 377.05 mL of Part B.
Try this example in the batch calculator →
How much extra should I allow?
Material can remain in cups and on tools, or be lost to spills. The amount depends on the project and process. Our example starts at 10%, which you can change or set to zero; it is not a universal requirement.
Irregular molds: use a known cavity volume
Rounded corners, relief details and irregular cavities can make a bounding rectangle overestimate volume. If you have reliable cavity-volume information, such as the mold supplier’s specification, choose Known volume in the batch calculator. Enter the combined resin + hardener volume for one piece at your intended fill level, before extra allowance.
80 mL per piece × 6 = 480 mL
With a user-selected 10% extra allowance, the mixed batch is 528 mL. At a product-specified 2:1 ratio by volume, that is 352 mL Part A and 176 mL Part B. The 80 mL input is an example, not an estimate for a particular mold.
Check whether a supplier’s amount describes one cavity or the whole mold. Use mL or US fluid ounces for liquid volume; grams and weight ounces need product-specific density information. This mode uses your supplied volume and does not model detailed 3D shapes or subtract embedded objects. You can combine known-volume entries with round and rectangular molds in the same batch.
Volume is not a pour-depth recommendation
Knowing the total amount does not tell you whether it can be mixed or poured in one batch. Follow the exact product’s mixing, working-time, temperature and layer-depth instructions.
Read weight versus volume before choosing a mixing ratio, or review our calculation method.