Epoxy Resin Calculator

Resin is a volume problem wearing a chemistry costume. Work out how much space the resin has to fill, convert that into millilitres, then split it by the mix ratio printed on your bottles.

The only genuinely awkward shape is the tumbler wrap, because you are not filling a space. You are coating a surface. That is the circumference of the cup multiplied by the height you are covering multiplied by how thick the coat is, which gives a thin shell rather than a solid volume.

1. Step 1 Volume of the shape rectangle = L × W × D cylinder = π × (d/2)² × h sphere = 4/3 × π × (d/2)³ tumbler wrap = π × d × h × coat_thickness
2. Step 2 Multiply by quantity and add waste total = volume × pieces × (1 + waste%) Waste is resin left in the cup and on the stick. It is real and it is always more than you expect.
3. Step 3 Convert to millilitres ml = cubic_inches × 16.387 In metric mode the dimensions are centimetres, and 1 cm³ is exactly 1 ml.
4. Step 4 Split by the mix ratio part_A = total × A ÷ (A + B) part_B = total × B ÷ (A + B)
5. Step 5 Convert to weight if you mix on scales grams = ml × 1.1 Most epoxies sit close to 1.1 g/ml. Check your data sheet if you need precision.

For example, a 4 × 4 in coaster mould poured 0.4 in deep is 6.4 cubic inches, which is 105 ml. Add 5% waste and you need 110 ml of mixed resin, 55 ml of each part at 1:1.

• Mixed resin density is taken as 1.1 g/ml, which is typical across craft and casting epoxies. Check your product data sheet if you are mixing by weight and need better than about 3% accuracy.
• The mix ratio is applied by volume. Several brands specify a different ratio by weight than by volume, for example 100:45 by weight but 2:1 by volume. Always use the figure that matches how you are measuring.
• The waste margin covers resin clinging to the mixing cup and stirring stick. It does not cover a spilled pour, a leaking mould, or a second coat.
• A tumbler wrap is modelled as a thin shell of even thickness. Real coats are thicker at the bottom where resin flows down, so treat the figure as a minimum.
• River table channels are modelled as a plain rectangular prism using the average width. Live-edge slabs curve, so measure the width at several points and use the middle value, and expect the true volume to be slightly lower.
• Deep-pour warnings trigger above 1.5 inches (about 4 cm) of pour depth, which is the common limit for tabletop resins. Deep-pour formulas on sale now are generally rated for 2 to 4 inches in a single layer, though a few are only good for 1 to 2. Follow the figure printed on your own product rather than the class.
• No allowance is made for objects embedded in the pour. Anything you place in the mould displaces resin, so the true requirement will be lower.