Epoxy is sold by volume, so the math is the volume of the pour: length times width times depth for a river channel or a mold, or the area of a circle times its depth. A US gallon is 231 cubic inches, so the cubic inches turn straight into gallons.
How to use this calculator
- Choose a rectangle or a circle. For a river table, measure the river channel, not the whole table.
- Enter the size and the depth of the pour. For a coating, the depth is the thickness of the coat.
- Check the extra under More options: one maker suggests 5 to 10 percent.
Worked examples
A river table channel
Shape: Rectangle · Size: 72 × 8 in · Depth: 1.5 in
- Mixed epoxy
- 4.11 US gallons
- Quarts
- 16.5
- Fluid ounces
- 527 fl oz
- Volume without the extra
- 864 cubic inches
A round tabletop coat
Shape: Circle · Diameter: 36 in · Depth: 0.125 in
- Mixed epoxy
- 0.61 US gallons
- Quarts
- 2.4
- Fluid ounces
- 78 fl oz
- Volume without the extra
- 127 cubic inches
A deep mold
Shape: Rectangle · Size: 12 × 12 in · Depth: 3 in
- Mixed epoxy
- 2.06 US gallons
- Quarts
- 8.2
- Fluid ounces
- 263 fl oz
- Volume without the extra
- 432 cubic inches
A bar top flood coat
Shape: Rectangle · Size: 96 × 24 in · Depth: 0.125 in
- Mixed epoxy
- 1.37 US gallons
- Quarts
- 5.5
- Fluid ounces
- 176 fl oz
- Volume without the extra
- 288 cubic inches
How deep can each pour be?
- Deep-pour casting resins are made for thick layers: one maker allows up to 2 inches per layer for a river table and 3 inches for castings.
- Table-top coating resins go on thin: the same maker allows up to 0.25 inch per coat.
- Pour thicker than the resin allows and it can overheat, crack or cure cloudy, so split a deep pour into layers.
Mixing and pouring
The result is resin and hardener together. Mix them in the ratio on your kit, by volume or by weight as the maker says, and mix only what you can pour before it starts to set.
Seal the wood with a thin coat first, so air in the grain does not bubble up through the pour, and tape the mold edges well: epoxy finds every gap.
Common questions
How much epoxy do I need for a river table?
Measure the river channel's length, average width and depth, multiply them for cubic inches, and divide by 231 cubic inches for gallons. Add 5 to 10 percent extra. The calculator does this for you.
How do I calculate epoxy for a coating?
Use the same volume math with the coat's thickness as the depth: area times thickness. A thin coat over a large table top still takes more than you might expect.
Can I pour epoxy two inches deep?
Only with a deep-pour resin made for it. One maker allows up to 2 inches per layer for river tables; coating resins go on much thinner.
How much extra epoxy should I mix?
One maker suggests 5 to 10 percent extra for what stays on the stir stick and in the cup, and more for a rough or porous surface.