Resin Mold Volume Calculator: ml, Grams & All Shapes
Calculate exact resin for any silicone mold or custom shape — sphere, cylinder, cube, rectangle, cone, pyramid, and irregular forms. Works for silicone molds, wood forms, and custom cavities. Instant ml and grams output. No sign-up.
💡 Tip: Measure with digital calipers for precision. Shop quality silicone molds.
Example calculation
Let's calculate volume for a cylindrical coaster mold:
| Parameter | Value |
|---|---|
| Mold shape | Cylinder (round) |
| Diameter | 100mm (10cm) |
| Height/Depth | 8mm (0.8cm) |
| Add 10% buffer | Yes |
| Resin needed | 69 ml (or 72 grams) |
Formula: π × (50mm)² × 8mm = 62,832 mm³ ÷ 1000 = 62.8ml + 10% buffer = 69ml
Why resin volume and weight differ: density explained
Epoxy resin is denser than water. Most craft epoxy resins have a density of 1.05–1.15 g/ml, meaning one milliliter of mixed resin weighs more than one gram. This calculator uses 1.05 g/ml as the standard conversion, which is accurate for most table top and casting resins.
In practice: if your mold needs 100 ml of resin, you need to mix approximately 105 grams of combined resin and hardener. When measuring on a digital scale, always weigh in grams — volume measurements in cups are less accurate because resin viscosity affects how it fills a graduated container.
Some thicker resins (deep pour, casting) run closer to 1.1 g/ml. Check your brand's technical data sheet for the exact density if precision matters for your project.
Mold volume formulas
Cylinder (round coasters, tumblers)
Formula: π × radius² × height
Example: Diameter 100mm, height 10mm
π × 50² × 10 = 78,540 mm³ = 78.5 ml
Sphere (round balls, ornaments)
Formula: (4/3) × π × radius³
Example: Diameter 60mm
(4/3) × π × 30³ = 113,097 mm³ = 113.1 ml
Cube (square molds)
Formula: side × side × side
Example: 50mm cube
50 × 50 × 50 = 125,000 mm³ = 125 ml
Rectangle / Box (trays, pendants)
Formula: length × width × height
Example: 80mm × 50mm × 15mm
80 × 50 × 15 = 60,000 mm³ = 60 ml
Cone / Pyramid (pointed decorations)
Formula: (1/3) × π × radius² × height
Example: Base diameter 60mm, height 80mm
(1/3) × π × 30² × 80 = 75,398 mm³ = 75.4 ml
Hemisphere (half-sphere domes)
Formula: (2/3) × π × radius³
Example: Diameter 60mm
(2/3) × π × 30³ = 56,549 mm³ = 56.5 ml
💡 For accurate measurements use digital calipers — small errors in diameter compound significantly in volume calculations (a 2mm error on a 60mm sphere = ~10% volume difference).
Common resin mold sizes and their volumes
Use this reference table to check your mold's typical volume before measuring. All values are approximate — measure your specific mold for accuracy.
| Mold Type | Typical Size | Volume (ml) | Weight (grams) |
|---|---|---|---|
| Round coaster | 90mm diameter × 8mm deep | 51 ml | 54 g |
| Round coaster (large) | 100mm diameter × 10mm deep | 79 ml | 83 g |
| Square coaster | 100mm × 100mm × 8mm | 80 ml | 84 g |
| Small pendant (round) | 25mm diameter × 8mm deep | 4 ml | 4 g |
| Medium pendant (round) | 40mm diameter × 10mm deep | 13 ml | 14 g |
| Sphere (small) | 50mm diameter | 65 ml | 68 g |
| Sphere (medium) | 65mm diameter | 144 ml | 151 g |
| Sphere (large) | 80mm diameter | 268 ml | 281 g |
| Keychain (rectangle) | 50mm × 30mm × 6mm | 9 ml | 9 g |
| Bookmark (standard) | 150mm × 50mm × 5mm | 38 ml | 40 g |
| Small tray | 150mm × 100mm × 15mm | 225 ml | 236 g |
| Cube (small) | 40mm × 40mm × 40mm | 64 ml | 67 g |
💡 All volumes include 0% buffer — use the calculator above with the buffer checkbox for your actual pour amount. Resin density assumed at 1.05 g/ml.
Accurate mold measuring tips
📏 Measure the cavity, not the mold
Always measure the inside space where resin goes, not the outside dimensions of the silicone mold itself.
💧 Use water displacement method
For irregular molds, fill with water, pour into a measuring cup. The water volume equals resin volume needed.
🔢 Measure in millimeters
Millimeters provide better accuracy than inches for small molds. 1ml = 1 cubic centimeter = 1,000 cubic mm.
✅ Double-check measurements
Measure twice, especially for expensive resin projects. Being off by 5mm can waste 10-20ml of resin.
🛒 Shop molds: Jewelry Molds • Coaster Molds • Tray Molds
Formulas verified against standard geometric volume equations. Density conversion (1.05 g/ml) based on manufacturer technical data sheets for common craft epoxy resins including ArtResin, MAS Epoxies, and TotalBoat.
Mold volume calculator FAQs
How do I calculate mold volume for resin?
Measure your mold dimensions (diameter, length, width, height depending on shape), then use the appropriate formula. For a sphere: (4/3) × π × radius³. For a cylinder: π × radius² × height. For a cube or rectangle: length × width × height. Our calculator does the math automatically—just enter your measurements and select your mold shape.
How do I convert ml to grams for resin?
Multiply milliliters by 1.05 to convert to grams. Most epoxy resins have a density of 1.05 g/ml, meaning 100ml of resin weighs approximately 105 grams. This calculator automatically converts between ml, grams, and ounces. When measuring on a digital scale, use grams for the most accuracy.
What if my mold has an irregular shape?
For irregular molds, use the water displacement method: fill the mold with water, pour the water into a measuring cup, and note the volume in ml. This gives you the exact amount of resin needed. Alternatively, measure the longest dimensions and use our Custom shape option with an 85% reduction factor to approximate the volume.
Should I add extra resin to my calculated volume?
Yes, always add 10-15% extra resin. This accounts for waste in mixing cups, resin stuck to stirring tools, and air bubbles you'll pop. Use the buffer checkbox in this calculator to automatically add 10% extra. For small molds under 50ml, this buffer is especially important since being short by even 5ml can mean an incomplete pour.
How do I measure mold dimensions accurately?
Use digital calipers or a ruler to measure the inside cavity of the mold, not the outside dimensions. For round molds, measure diameter across the widest point. For depth, measure from the top edge to the bottom of the cavity. Measuring in millimeters provides the most accuracy—10mm is much more precise than rounding to the nearest 1/4 inch.
Can I reuse resin molds?
Yes, quality silicone molds can be reused 50-100+ times if cared for properly. Use mold release spray for easier demolding, wash with soap and water after each use, and store flat to prevent warping. Avoid sharp tools when demolding—gently flex the mold instead.
What's the difference between volume and weight for resin?
Volume measures space (ml, oz), while weight measures mass (grams, pounds). Resin is measured by weight for mixing accuracy because volume can vary with air bubbles and temperature. However, mold capacity is measured in volume (ml). Use this calculator to convert mold volume to resin weight, then use our Small Batch Mixing Calculator to get Part A and Part B weights.