🧪 Resin Casting Volume Calculator

Enter your mold shape, dimensions, and mix ratio to calculate the resin volume needed, Part A/B amounts, and estimated weight.

Mold Shape

Length (cm)

Width (cm)

Height (cm)

Mix Ratio A (by volume)

Mix Ratio B (by volume)

Overage (%)

Resin Volume Needed (with overage)

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Mold Volume — Part A Amount — Part B Amount — Estimated Weight (at ~1.1g/mL) —

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GUIDE

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Mold Volume Formulas

The volume (cm³ = mL) formula depends on your mold shape.

Shape	Formula
Rectangular / Box	V = Length × Width × Height
Cylinder	V = π × Radius² × Height
Sphere	V = (4/3) × π × Radius³
Half-Sphere	V = (2/3) × π × Radius³

For example, a box mold that is 10cm × 8cm × 5cm has a volume of 10×8×5 = 400cm³ (= 400mL).

How Overage and A/B Mix Amounts Are Calculated

Mixing exactly the mold volume often leaves you short because some resin always sticks to the mixing cup and stir stick, so it is common resin-casting-community advice to mix about 10% extra. Resin volume needed = mold volume × (1 + overage% / 100). Dividing this by your mix ratio (A:B) gives the amount of each part. For example, at a 400mL mold volume with 10% overage, you need 440mL of resin; at a 1:1 ratio, that is 220mL of Part A and 220mL of Part B. Most art/casting epoxy resins use a 1:1 ratio by volume by default, but some brands use 2:1 or 100:44 by weight — always check your specific product's datasheet and override the ratio fields as needed. Weight is estimated using a typical cured epoxy resin density of about 1.1g/mL, a commonly cited average that varies by brand.

Frequently asked questions

Why should I mix more resin than the exact mold volume?

Resin sticks to the mixing cup, stir sticks, and measuring tools, and some is lost while removing bubbles, so the amount you can actually pour is always a bit less than the calculated volume. Mixing about 10% extra accounts for this.

Is the mix ratio always 1:1?

No. 1:1 is common for art/casting epoxy resins, but some products use 2:1 or 100:44 by weight. Always check your specific resin product's datasheet and adjust the ratio fields in this calculator to match.

Why is the estimated weight only an estimate?

The density of cured epoxy resin varies by product and by additives (pigments, glitter, etc.), so this calculator uses a commonly cited average density of about 1.1g/mL. Weigh your actual mix if you need an exact figure.