About the Epoxy Calculator
This epoxy calculator tells you how much mixed resin a project needs before you open a kit. Choose a pour (river tables, molds, bar tops and flood coats measured by length, width and depth) or a floor/surface coating measured by area and film thickness in mils, and the calculator returns gallons, liters and fluid ounces, plus the split between resin and hardener at your product’s mix ratio.
It is meant for woodworkers planning a river table, makers casting in molds, and DIYers coating a garage or basement floor. Running short halfway through a pour leaves a visible layer line, and mixing too much wastes an expensive product that cannot be saved once catalyzed, so an accurate number up front matters.
Volumes are based on the geometry you enter plus a waste allowance for mixing cups, drips, wood absorption and uneven substrates. Always check the maximum pour depth on your product’s data sheet: deep-pour casting resins and thin coating resins are not interchangeable, and thick pours may need to be done in several layers.
With the default inputs, the epoxy needed (with waste) is 3.43 gal. Change any value above to recalculate instantly.
How to use the epoxy calculator
- 1Pick a pour (river table, mold, flood coat) or a floor/surface coating.
- 2Enter the pour dimensions in inches, or the area and mils per coat for a coating.
- 3Choose your product’s resin-to-hardener mix ratio by volume.
- 4Set a waste allowance — 10% for most jobs, more for porous wood or rough concrete.
- 5Read the total gallons and the Part A / Part B split, then buy the next kit size up.
Formula and method
For a pour, the volume in cubic inches is length × width × depth, and one US gallon is exactly 231 cubic inches. For a coating, the area in square feet is converted to square inches (× 144) and multiplied by the film thickness in inches (mils ÷ 1000) and the number of coats — which is why one gallon covers about 1,604 sq ft at 1 mil.
A waste percentage is then added for material left in mixing containers, drips, absorption into wood and uneven substrates. The total is split into Part A (resin) and Part B (hardener) using the volumetric mix ratio: with a 2:1 product, two-thirds of the mix is resin and one-third is hardener. Products mixed by weight need their own weight ratio from the data sheet.
- L, W, D
- Pour length, average width and depth in inches
- A
- Coated area in square feet
- mils
- Wet film thickness per coat (1 mil = 0.001 in)
- 231
- Cubic inches in one US gallon
Worked examples
River table: 48 in long, 10 in wide, 1.5 in deep
The river holds 48 × 10 × 1.5 = 720 cubic inches, or 720 ÷ 231 = 3.12 gallons. Adding 10% waste gives about 3.43 gallons of mixed epoxy — 1.71 gallons each of resin and hardener at 1:1 — costing roughly $206 at $60 per gallon.
Two-car garage floor, 400 sq ft, two 10-mil coats
400 sq ft × 144 = 57,600 sq in; × 0.010 in × 2 coats = 1,152 cubic inches, or 4.99 gallons. With 10% extra for a slightly porous slab you need about 5.5 gallons of mixed product.
Tabletop flood coat 24 × 36 in, 1/8 in thick, 2:1 resin
A 1/8-inch flood coat over 24 × 36 inches is 108 cubic inches (0.47 gal). With 10% waste you mix about 0.51 gallon (66 fl oz): two parts resin (0.34 gal) to one part hardener (0.17 gal).
Frequently asked questions
How much epoxy do I need for a river table?+
Multiply the river’s length × average width × depth in inches and divide by 231 to get gallons, then add about 10% for waste and soak-in. A 48 × 10 × 1.5 inch river needs roughly 3.4 gallons of mixed epoxy.
How many square feet does a gallon of epoxy cover?+
One gallon covers about 1,604 sq ft at a 1-mil film. So at 10 mils it covers roughly 160 sq ft per coat, and a 1/8-inch (125-mil) flood coat covers only about 12.8 sq ft per gallon.
Does the mix ratio change how much epoxy I need?+
No — the total mixed volume depends only on the space you are filling. The ratio only decides how that total splits between Part A resin and Part B hardener, e.g. 2:1 means two-thirds resin, one-third hardener.
How deep can I pour epoxy in one layer?+
It depends on the product. Coating and tabletop resins are typically limited to around 1/8–1/4 inch per layer, while deep-pour casting resins can often go 1–2 inches or more. Exceeding the limit can cause overheating, cracking or yellowing.
How much extra epoxy should I buy?+
Plan on 10–15% extra for mixing losses and drips; use more for live-edge wood that soaks up resin or molds with leaks. Mix in batches so leftover capacity stays unmixed and usable.