How to calculate resin volume
Resin volume is the space you're filling: the area of the shape times the pour depth.
| Shape | Volume formula |
|---|---|
| Rectangle / square | length × width × depth |
| Circle / cylinder | 3.1416 × (diameter ÷ 2)² × depth |
| Triangle | ½ × base × height × depth |
Then convert to the units on your resin bottle:
fl oz = cubic inches ÷ 1.805 · ml = cubic centimeters · grams ≈ ml × 1.1
Worked example: four round coasters
Each coaster mold is 4" across and you pour 1/4" deep. Volume = 3.1416 × 2² × 0.25 = 3.14 cubic inches, or 3.14 ÷ 1.805 = 1.74 fl oz per coaster. Four coasters need 6.96 fl oz; add 10% for the cup and stir stick and mix about 7.7 fl oz. With a 1:1 ratio, that's about 3.8 fl oz of resin and 3.8 fl oz of hardener.
Tips for mixing the right amount
- Mix at least the minimum batch listed on your product — very small batches may not cure properly.
- Don't mix more than you can pour before the working time runs out. For big pours, mix in batches.
- Adding alcohol ink or pigment? Check your brand's limit for colorants — too much can stop the resin curing properly. A few drops of alcohol ink is usually enough.
- Silicone molds are often slightly smaller inside than their outside size — measure the cavity.
- Irregular molds: fill the mold with water, pour the water into a measuring cup, and use that volume (dry the mold completely afterwards).
Questions, answered
How do I calculate how much resin I need?
Multiply length × width × depth to get the volume. In inches, divide cubic inches by 1.805 to get US fluid ounces; in centimeters, cubic centimeters equal milliliters. For a round mold use π × radius² × depth. Add about 10% for spills and resin left in the cup.
How much resin do I need for a coaster?
A 4" round coaster poured 1/4" deep holds about 3.1 cubic inches, or roughly 1.7 fl oz (51 ml) of mixed resin. A set of four needs about 7.7 fl oz including a 10% margin.
How much resin do I need to coat a painting or tray?
ArtResin bases its coverage on a 1/8" (3 mm) flood coat; some resin makers suggest a thinner coat. A 12" × 12" surface at 1/8" needs about 18 cubic inches, or 10 fl oz (295 ml) of mixed resin. Choose "Coating 1/8 inch" in the depth field, or enter your product's recommended thickness.
Should I measure resin by volume or by weight?
Follow your product label. Some epoxies are mixed 1:1 or 2:1 by volume, others give a ratio by weight such as 100:45. Resin and hardener often have different densities, so a ratio by weight and the same ratio by volume are not interchangeable.
How deep can I pour resin in one layer?
Coating resins are usually limited to about 1/8"–1/4" per layer, while deep-pour casting resins can go 1–2" or more. Pouring too deep at once can overheat, crack or yellow. Check the maximum pour depth on your product.
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