Epoxy Resin Calculator

• How to Use the Epoxy Resin Calculator
• Worked Example: A 48 by 24 Inch Tabletop
• The Epoxy Volume Formula
• Epoxy Coverage per Gallon by Thickness
• Seal Coat vs Flood Coat: Budget for Both
• Mix Ratios: Splitting Part A and Part B
• River Tables and Deep Pours
• FAQs

Epoxy is sold by the kit and wasted by the mistake. Mix too little and you are scrambling to blend a second batch while the first one gels on your tabletop; mix far too much and expensive resin hardens in the bucket. The difference between a smooth pour and a stressful one is a two-minute calculation done before anything is opened. This epoxy resin calculator works out exactly how much mixed epoxy your project needs from its length, width, and pour depth, adds a waste allowance you control, and then splits the total into Part A resin and Part B hardener for the mix ratio your product uses — 1:1, 2:1, or 3:1 — so the measuring cups come out right the first time.

How to Use the Epoxy Resin Calculator

Measure the area the epoxy will actually cover, in inches: the length and width of the tabletop, countertop, or mold. Then enter the pour depth — the thickness of the epoxy layer itself, not the thickness of the wood under it. The standard depths are 1/16 inch (0.0625) for a seal coat, 1/8 inch (0.125) for the usual flood coat on tabletops and bar tops, and 1 to 2 inches for a deep pour with a casting resin. Choose the mix ratio printed on your kit; most tabletop epoxies are 1:1 by volume, many deep-pour resins are 2:1, and some are 3:1.

Set the waste allowance — 10 percent is a good default, and the sections below explain why edges and porous wood argue for it. The calculator returns the total mixed epoxy in fluid ounces, gallons, and liters, and the amount of each part to measure.

Worked Example: A 48 by 24 Inch Tabletop

Take a coffee table top or small desk, 48 inches long by 24 inches wide, getting a standard 1/8 inch flood coat of a 1:1 tabletop epoxy, with the default 10 percent waste allowance:

So a one-gallon 1:1 kit — 64 ounces of each part — covers this top with room to spare for the seal coat underneath it. Notice how quickly the ounces move with depth: the same top poured 1 inch thick as a casting would need nearly 640 ounces before waste — about five gallons. Depth, not area, is what empties kits.

The Epoxy Volume Formula

Epoxy math is volume math, and it rests on one fixed conversion: a US gallon is exactly 231 cubic inches, and a fluid ounce is 231 ÷ 128 of that. The whole calculation is:

Volume (cubic inches) = length × width × depth

Gallons = cubic inches ÷ 231 and fluid ounces = cubic inches × 0.5541

That is all the calculator does, plus the waste percentage you choose and the ratio split. Because the formula is exact, any disagreement between the calculator and a manufacturer’s coverage claim comes from the assumptions, not the arithmetic — the manufacturer may be quoting a slightly thinner coat, rounding coverage upward, or leaving out waste. When your calculation and a kit’s marketing number differ, trust the geometry and the waste allowance: running short mid-pour is a far worse outcome than a leftover half-cup of resin. For tops with cutouts or an L-shape, our surface area calculator breaks the area into rectangles before you start.

Epoxy Coverage per Gallon by Thickness

The table below is the theoretical coverage of one gallon of mixed epoxy — 231 cubic inches spread at a perfectly even thickness, before waste, runoff, and absorption:

The 1/8 inch line is the one the whole industry quotes: about 12 to 13 square feet per gallon for a flood coat. Real projects land lower — plan on roughly 10 to 11 square feet per gallon once the epoxy that runs over the edges, stays in the mixing cup, and soaks into the wood is counted, which is exactly what the calculator’s 10 percent waste allowance is for. If your pour is meant to drip over and coat the edges, add more: edge runoff on a free-standing top is significant, and some makers suggest adding up to 30 percent when every edge is flooded.

Seal Coat vs Flood Coat: Budget for Both

Most wood projects need two pours, and the resin for both belongs in your order. A seal coat is a thin layer — brushed or spread at roughly a 1/16 inch equivalent — applied first to porous wood. Its job is to soak into the grain and seal the pores so air stops bubbling up into the main pour; raw wood, especially soft or spalted wood, can release bubbles for hours otherwise. A gallon of epoxy seals roughly 25 square feet at that thickness, and manufacturers quote 30 to 40 square feet per gallon for a brushed film coat.

The flood coat follows once the seal coat has gelled — a self-leveling 1/8 inch pour that gives the glass-like surface. Run the calculator twice, once for each coat, and order for the sum. Skipping the seal coat to save resin is the classic false economy: the bubbles it prevents appear in the flood coat, where they are much harder to remove.

Mix Ratios: Splitting Part A and Part B

The calculator’s split assumes your ratio is measured by volume, which is how most consumer kits are specified. Two cautions keep that split honest. First, some professional products specify the ratio by weight instead, and because resin and hardener have different densities, a by-weight 2:1 is not the same as a by-volume 2:1 — read your product’s data sheet and follow its stated basis, using graduated mixing cups for volume or a scale for weight.

Second, the ratio is not a seasoning to adjust: too little hardener leaves the pour permanently soft or sticky, too much can make it brittle, discolored, or prone to cracking, and “a bit extra so it cures faster” does not work — cure speed is set by the product’s chemistry and the room temperature, not by overdosing Part B. Measure both parts accurately, mix thoroughly while scraping the sides and bottom of the cup, and pour into a second clean cup and mix again if your product recommends the two-cup method. Nearly every failed pour traces back to measurement or mixing, not to the resin itself.

River Tables and Deep Pours

For a river table, the “width” in the calculator is the width of the river channel, not the whole table. Measure the channel at several points, use its average width, and enter the full table length and your pour depth. Irregular live edges make the true volume fuzzy in both directions, so raise the waste allowance to 15 or 20 percent rather than the usual 10 — resin finds every low corner of a natural edge. Depth discipline matters even more: tabletop coating epoxies are typically limited to about 1/8 inch per layer, while deep-pour casting resins are commonly rated for pours of up to 2 inches at a time (a few go deeper — the data sheet for your product is the authority).

Epoxy cures by an exothermic reaction, meaning it generates its own heat; a pour thicker than its rating can overheat as it cures and yellow, crack, foam, or even smoke. Deep projects are built in successive layers, each poured once the previous one has gelled but not fully cured, and the calculator sizes each layer separately if you enter the layer depth. If the pour tops a workbench or outdoor bar you are building yourself, our deck calculator sizes the lumber for the frame underneath.

FAQs

How much epoxy do I need for a tabletop?

Multiply the top’s length by its width by the coat thickness in inches, then divide by 231 for gallons. A 48 by 24 inch top at the standard 1/8 inch flood coat needs 144 cubic inches — 0.62 gallons, or 79.79 fluid ounces before waste, 87.77 ounces with a 10 percent allowance. The industry shortcut says the same thing: one gallon covers about 12 to 13 square feet at 1/8 inch.

How do I calculate epoxy for a river table?

Measure the river channel, not the whole table: use the table’s length, the channel’s average width measured at several points, and the pour depth. Run those numbers through the epoxy resin calculator with the waste allowance raised to 15 or 20 percent, because live edges and irregular banks make the volume uncertain. If the pour is deeper than your resin’s per-layer limit, calculate and pour it in layers.

What does a 2:1 mix ratio mean in ounces?

It means two parts resin to one part hardener, by volume (unless your product specifies by weight). For a 90 fl oz total batch, that is 60 fl oz of Part A and 30 fl oz of Part B. The calculator performs this split for 1:1, 2:1, and 3:1 ratios automatically. Measure exactly — an off-ratio mix is the most common cause of epoxy that never fully hardens.

How deep can I pour epoxy in one pour?

It depends entirely on the product type. Tabletop and coating epoxies are typically limited to about 1/8 inch per layer; deep-pour casting resins are commonly rated up to 2 inches per pour, with a few specialty products rated deeper. Exceeding the rating risks an overheating (exothermic) cure that can yellow, crack, or foam the pour. Always follow the maximum depth on your product’s data sheet.

Why did my epoxy stay sticky?

Almost always one of three causes: the ratio was measured inaccurately, the two parts were not mixed thoroughly (unmixed resin clinging to the cup’s sides and bottom is the classic culprit), or the room and materials were too cold for a proper cure. A thin, correctly mixed fresh layer over the top sometimes rescues a tacky surface once the cause is fixed, but soft, rubbery epoxy usually has to be removed and re-poured.

Does the calculator work in liters and milliliters?

Yes — alongside fluid ounces and gallons it reports the total in liters (the 48 by 24 inch worked example needs 2.60 liters). For milliliters, multiply the liter figure by 1,000. If your kit is sold in liters and specifies its ratio by volume, the Part A and Part B splits convert the same way: multiply each ounce figure by 29.5735 to get milliliters.

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