How to Use the Epoxy Resin Calculator
Step 1: How to measure
Measure the surface you plan to coat or the mold you plan to fill at its longest and widest points. For rectangular table tops and molds, measure inside the form walls, not the outside, because the epoxy only fills the interior. For garage floors, measure wall to wall in feet and subtract large permanent obstructions such as built-in cabinets.
Thickness is the most important number. A flood coat on a table top is usually 1/8 inch (0.125 in). A deep pour casting resin is typically poured 1 to 2 inches per layer depending on the product. Garage floor coatings are measured in mils — 10 mils is 0.01 inch, a common single-coat thickness. For irregular river channels, take three width measurements and average them.
Step 2: The exact formula
Epoxy volume is simple geometry: length × width × thickness gives cubic inches. One US liquid gallon equals 231 cubic inches, and one gallon contains 128 fluid ounces. Because nearly every kit is sold as combined resin plus hardener volume, the result is the total mixed volume you need.
We multiply by 1.10 when the waste toggle is on to cover epoxy left in mixing cups, absorbed by porous wood, and dripped over edges. Seal-coating raw wood first reduces absorption significantly.
Gallons = (L in × W in × Thickness in × 1.10) ÷ 231 Fluid oz = Gallons × 128
Pro DIY tips
- Always seal-coat raw wood with a thin layer first — it stops air bubbles from rising out of the grain into your flood coat.
- Never pour a table-top resin deeper than the manufacturer's rating; excess thickness can overheat, yellow, or crack.
- Work at 70–80°F. Cold resin is thick, traps bubbles and cures slowly; hot resin shortens working time dramatically.
- Level your mold or table with a long level before pouring — epoxy self-levels to gravity, not to your project.
- For garage floors, profile the concrete with diamond grinding or acid etching and do a moisture test before coating.
Frequently asked questions
How much epoxy do I need for a 2-car garage?
A typical 20×20 ft 2-car garage at 10 mils needs about 2.75 gallons of mixed epoxy per coat with 10% waste. Most systems recommend a base coat plus a top coat.
How many ounces of epoxy per square foot?
At 1/8 inch thick, one square foot needs about 10 fl oz (0.078 gallons) of mixed epoxy before waste.
Can I pour deep pour epoxy all at once?
Only up to the maximum depth listed by the manufacturer — often 1 to 2 inches per pour. Deeper projects must be poured in layers after each layer reaches the recommended stage.
Does the calculator include resin and hardener?
Yes. The result is total mixed volume. If your kit is 1:1, half is resin and half is hardener; for 2:1 kits, two-thirds is resin.
Why add 10% waste?
Epoxy clings to mixing buckets, soaks into wood pores and runs off edges. A 10% buffer prevents running short mid-pour, which can leave visible lines.