How the calculator works
Epoxy is sold and measured by volume, so the calculator first finds the volume of the space you are filling, in cubic inches.
- Rectangle: length × width × depth.
- Round: π × (diameter ÷ 2)² × depth.
- Tabletop coat: length × width × coat thickness. A self-leveling flood coat is usually about ⅛ inch.
- Subtract the wood, stones or inserts that sit in the pour, then add waste for resin left in the cups, on stir sticks and dripping off edges (10 percent by default).
It then converts the volume: cubic inches ÷ 231 = US gallons, gallons × 128 = fluid ounces, gallons × 3.785 = liters. For the two parts, a 1:1 mix is half and half, a 2:1 mix is two-thirds Part A and one-third Part B, and a 3:1 mix is three-quarters and one-quarter. The weight uses a density of 1.1 g/mL, a common middle value; the real figure is on your product's data sheet.
Epoxy for tabletop coats
Mixed resin for a flood coat of ⅛ inch and a thicker ¼ inch coat, including 10 percent waste. It does not include a seal coat or resin for the edges.
| Top size | Area | ⅛ in coat | ¼ in coat |
|---|---|---|---|
| 24 × 24 in | 4 sq ft | 44 fl oz (0.34 gal, 1.3 L) | 88 fl oz (0.69 gal, 2.6 L) |
| 24 × 48 in | 8 sq ft | 88 fl oz (0.69 gal, 2.6 L) | 176 fl oz (1.37 gal, 5.2 L) |
| 30 × 60 in | 12.5 sq ft | 137 fl oz (1.07 gal, 4.1 L) | 274 fl oz (2.14 gal, 8.1 L) |
| 36 × 72 in | 18 sq ft | 197 fl oz (1.54 gal, 5.8 L) | 395 fl oz (3.09 gal, 11.7 L) |
| 42 × 84 in | 24.5 sq ft | 269 fl oz (2.1 gal, 7.9 L) | 538 fl oz (4.2 gal, 15.9 L) |
| 48 × 96 in | 32 sq ft | 351 fl oz (2.74 gal, 10.4 L) | 702 fl oz (5.49 gal, 20.8 L) |
Epoxy for river tables
Mixed resin for the river only, from its length and average width, including 10 percent waste. Live edges wander, so measure the gap in several places and average them.
| River length | Average river width | 1 ½ in deep | 2 in deep |
|---|---|---|---|
| 48 in | 6 in | 2.06 gal (7.8 L) | 2.74 gal (10.4 L) |
| 60 in | 8 in | 3.43 gal (13 L) | 4.57 gal (17.3 L) |
| 72 in | 8 in | 4.11 gal (15.6 L) | 5.49 gal (20.8 L) |
| 84 in | 10 in | 6 gal (22.7 L) | 8 gal (30.3 L) |
| 96 in | 12 in | 8.23 gal (31.1 L) | 10.97 gal (41.5 L) |
Example: a river table with 2:1 resin
The mold is 72 × 30 inches and the slabs are 1 ½ inches thick. Two slabs, each about 11 inches wide on average, sit in it, leaving a river about 8 inches wide.
- The whole mold: 72 × 30 × 1.5 = 3,240 cubic inches.
- The wood: 72 × 11 × 1.5 = 1,188 cubic inches per slab, 2,376 for both.
- Space to fill: 3,240 − 2,376 = 864 cubic inches. With 10 percent waste: 950.4 cubic inches.
- In gallons: 950.4 ÷ 231 = 4.11 gallons (527 fluid ounces, 15.6 liters).
- At 2:1 by volume: 2.74 gallons of Part A and 1.37 gallons of Part B.
- The mixed resin weighs about 38 pounds at 1.1 g/mL.
A 1 ½-inch river calls for a deep-pour casting resin. If its data sheet allows less than that per layer, pour in two or more layers, waiting between them as the instructions say.
Tips before you mix
- Check what a kit's size means. Some kits are sold by the combined volume of both parts and some by each part. Read the label before you decide how many to buy.
- Seal the wood first. Porous wood releases air into the resin. A thin seal coat brushed on and allowed to set cuts down on bubbles in the main pour.
- Seal the mold. Run silicone or tape along every seam. A slow leak can drain a surprising amount of resin overnight.
- Mix only what you can pour. Resin left in a deep cup heats up faster than the same resin spread thin. Mix in batches you can pour well within the working time on the data sheet.
- Measure carefully. Use graduated cups, scrape the sides and bottom while you mix, and do not guess the ratio. Off-ratio epoxy may stay soft or tacky.
- Respect the temperature range. Cold resin is thick and traps bubbles; a warm room shortens the working time. Use the range on the product's instructions.
- Protect yourself. Wear nitrile gloves and eye protection, ventilate the room, and follow the safety data sheet.
Frequently asked questions
How much epoxy do I need for a river table?
Multiply the river's length by its average width and its depth in inches, divide by 231 to get gallons, and add about 10 percent. A river 72 inches long, 8 inches wide on average and 1 ½ inches deep is 864 cubic inches, or 3.74 gallons; with 10 percent extra, mix about 4.1 gallons.
How much epoxy does it take to coat a table top?
A flood coat about ⅛ inch thick on a 2 × 4 foot top takes about 88 fluid ounces (0.69 gallon) including 10 percent for waste. Bare wood usually needs a thin seal coat first, and resin that runs over the edges needs extra.
How do I convert cubic inches of resin to gallons?
Divide by 231, because one US gallon is 231 cubic inches. For fluid ounces, multiply cubic inches by 0.554. One liter is 61.02 cubic inches.
How thick can I pour epoxy in one layer?
It depends on the product. Tabletop and coating epoxies are made for thin layers, typically about ⅛ inch per coat. Deep-pour casting resins can go much thicker, but each product has its own maximum per layer on its data sheet. Pouring deeper than that risks overheating, cracking and yellowing.
Should I mix epoxy by volume or by weight?
Follow the manufacturer's instructions. Most 1:1 and 2:1 hobby epoxies are measured by volume, and the two parts often have different densities, so the same ratio by weight would be wrong. This calculator splits Part A and Part B by volume.
How much does a gallon of epoxy weigh?
About 9 pounds at a typical density of 1.1 grams per milliliter. Densities vary by product, so check the technical data sheet if you need an exact weight.
Last updated October 17, 2026.