How the epoxy resin calculator works
Choose the shape of your project (a tabletop or tray, a round piece such as a coaster, or a river table), enter the size and the depth of the pour, and the calculator tells you how much epoxy to mix. It adds a margin for waste, splits the total into resin (part A) and hardener (part B) using your mix ratio, estimates the weight, shows how many pours you need, and suggests kit sizes to buy.
The volume is simply length × width × depth for a rectangle, or π × radius² × depth for a round piece. The calculator converts it to fluid ounces, gallons, millilitres or litres.
How much epoxy do you need?
| Project | Size | Epoxy needed |
|---|---|---|
| Flood coat on a tabletop | 24 × 48 in, 1/8 in deep | about 80 fl oz, or 88 fl oz with 10% extra |
| 4 round coasters | 4 in across, 1/4 in deep | about 7 fl oz, or 8 fl oz with 10% extra |
| River table | 48 in long, 4 in wide, 2 in deep | about 1.7 gal, or 1.8 gal with 10% extra |
A useful rule is that 1 gallon covers about 12 sq ft at 1/8 in deep.
Which type of epoxy should you use?
- Tabletop or coating epoxy is for thin coats of about 1/8 in on countertops, bars and tabletops. It self-levels and cures hard and glossy.
- Casting or art resin is for pours up to about 1/2 in deep, such as coasters, jewellery and trays.
- Deep pour epoxy cures slowly, so it can be poured up to about 2 in deep in one go without overheating. It is the choice for river tables.
The depth limits depend on the brand. Always read the label for the maximum depth per pour.
Why is the pour depth so important?
Epoxy gives off heat as it cures. In a thick layer, the heat cannot escape, and the epoxy can overheat, crack, yellow, or even smoke. Thin-coat epoxy poured deep will do this, which is why the calculator tells you how many layers you need. Wait until each layer is tacky, but not hard, before you pour the next, so that they bond.
Mix ratio
Epoxy is sold with a fixed ratio of resin to hardener, usually 1:1 or 2:1 by volume. Measure carefully, because the wrong ratio gives a soft, sticky finish that will not cure. Mix for the full time on the label, and scrape the sides and bottom of the container.
Worked examples
A 24 × 48 in tabletop with a 1/8 in flood coat
The volume is 24 × 48 × 1/8 = 144 cubic inches, or about 80 fl oz. With 10% extra you need about 88 fl oz at a 1:1 ratio, which is 44 fl oz of resin and 44 fl oz of hardener.
Four 4 in round coasters, 1/4 in deep
Each coaster is about 3 cubic inches. For four, you need about 7 fl oz, or about 8 fl oz with 10% extra. A single 16 oz kit is plenty.
A river table, 48 in long, 4 in wide and 2 in deep
The volume is 384 cubic inches, which is about 1.7 gal. With 10% extra, plan on about 1.8 gal. Deep pour epoxy can be poured in one go at this depth.
Common mistakes
- Not allowing for waste. Some epoxy sticks to the cup and the stirring stick, and some runs over the edges.
- Pouring too deep in one go. Too much heat causes cracks and yellowing.
- Not sealing the wood. Air in the wood makes bubbles in the epoxy, so seal it with a thin coat first.
- Measuring the ratio wrong. It will stay soft and sticky.
- Not leveling the table. Epoxy runs downhill, and the surface will be uneven.
Tips
- Work in a room at 70 to 75°F (21 to 24°C). Cold epoxy is thick and full of bubbles.
- Seal the mold or the underside of the piece with tape to stop leaks.
- Pop surface bubbles with a heat gun or a torch, held a few inches away.
- Cover the piece while it cures, so that dust does not settle on the surface.
- Wear gloves and a respirator, and work in a room with good ventilation.
