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Resin Mold Volume Calculator
Silicone molds rarely list their volume. Fill the mold with water and weigh it, or measure a simple shape, to know exactly how much epoxy to mix.
Formula
Water method: 1 g of water ≈ 1 ml, so V (ml) ≈ grams of water
Rectangle: L × W × H Cylinder: π r² h
Sphere: 4/3 π r³ Cone: π r² h ÷ 3
V_total = V × cavities × (1 + waste%)The water method in short
- Place the empty mold on a kitchen scale and tare it.
- Fill it with water to the level you want the resin to reach.
- Read the weight in grams — that's approximately the volume in milliliters.
- Empty the mold and dry it completely; water contaminates epoxy.
Water at room temperature has a density very close to 1 g/ml, so the error is tiny for resin crafts. Full instructions: measuring mold volume with the water method.
Note that ounces on a scale are weight ounces; the calculator converts them separately from fluid ounces.
Unit conversions used
- 1 US gallon = 231 in³ = 128 US fl oz
- 1 US fl oz = 1.8047 in³ = 29.5735 ml
- 1 in³ = 16.387 ml; 1 ft³ = 1,728 in³ ≈ 7.48 gal
- Weight = volume (cm³) × density. Many mixed epoxies are roughly 1.05–1.2 g/cm³; the default 1.1 is an approximation — check your product's technical data sheet and edit the field.
Frequently asked questions
How do I know how much resin my mold holds?
Fill the mold with water, weigh the water in grams, and treat that number as milliliters. Then dry the mold fully before pouring resin.
Is 1 gram of water really 1 ml?
Very nearly. Water's density at room temperature is about 0.997–0.998 g/ml, so the difference is well under 1%.
Do I need more epoxy by weight than water?
Usually yes, because epoxy is typically denser than water (roughly 1.1 g/cm³ for many products). Mix by volume from the water reading, or multiply grams by your epoxy's density if you mix by weight.
Can I use rice instead of water?
Some people use rice or sand to avoid moisture, but they pack unevenly and are less accurate. Water gives a more precise reading if you dry the mold well.