Resin Casting Volume Calculator
Work out epoxy and hardener for a shaped mold: block, cylinder, sphere, dome, cone or pyramid.
Returns volume, the 1:1 or 2:1 split, and weight.
Resin casting volume comes from the shape of the mold, then splits into resin and hardener by the mixing ratio.
This page is for shaped molds, where getting the volume right means knowing the geometry. If you are pouring something flat instead, a tabletop coating, a tray, a river table, use the resin pour calculator, which is built around depth per layer and has the coating-versus-deep-pour warnings that matter for flat work.
Volume by shape:
| Shape | Formula |
|---|---|
| Rectangular block or cube | Length × Width × Height |
| Cylinder or disc | π × Radius² × Height |
| Sphere or ball | (4/3) × π × Radius³ |
| Dome or half sphere | (2/3) × π × Radius³ |
| Cone | (1/3) × π × Radius² × Height |
| Rectangular pyramid | (1/3) × Length × Width × Height |
Radius is half the diameter, and the calculator asks for the diameter because that is what you can actually measure across a mold. A sphere and a dome need nothing but that one number, so the height box is ignored for both.
Measure the inside of the mold. Silicone walls are easily 5 mm a side, and measuring the outside is the usual reason a first pour comes up short.
Converting volume to weight: Epoxy resin has a specific gravity of about 1.15, so 1 cubic centimetre weighs roughly 1.15 grams. A cubic inch is 16.4 cm³, which puts it at about 18.8 grams, or 0.66 ounces.
Common mixing ratios (by volume):
- Most craft epoxies: 1:1 (equal parts resin and hardener)
- Some industrial epoxies: 2:1 (two parts resin to one part hardener)
- Polyester resin: 100:1 to 100:2 (resin to catalyst by weight)
- Polyurethane resin: 1:1 by volume
Important considerations:
- Always mix 10-15% extra to account for mixing cup residue and small spills
- Temperature affects curing time: warmer = faster cure, cooler = slower cure
- Working time (pot life) ranges from 15-45 minutes for most craft epoxies
- Pour in layers for pieces thicker than 1 inch (2.5 cm) to prevent overheating
- Exothermic reaction: thick pours generate heat and can crack or yellow
Weight conversion (imperial):
- 1 cubic inch of epoxy ≈ 0.66 oz (18.8 g)
- 1 fluid ounce ≈ 1.8 cubic inches
Weight conversion (metric):
- 1 cubic centimeter of epoxy ≈ 1.15 grams
- 1 milliliter ≈ 1 cubic centimeter
Pro tip: Use a digital scale for accurate measurements. Volume measurements with cups are less precise and can cause improper curing.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.