Epoxy Resin Calculator: How Much Epoxy Do I Need?

Epoxy Resin Calculator

The core math: inches to ounces to gallons

Every mode in the calculator runs the same conversion chain. Multiply your dimensions in inches to get cubic inches of volume, then divide by 1.805, because one US fluid ounce occupies 1.805 cubic inches (1.8046875 exactly). Divide ounces by 128 for gallons, or multiply by 29.57 for milliliters. A US gallon is 231 cubic inches, which is why one gallon of mixed epoxy poured 1 inch deep covers only 1.6 square feet (231 ÷ 144 = 1.6). Spread that same gallon as a 1/8-inch flood coat and pure geometry says 12.8 square feet; manufacturers such as TotalBoat quote roughly 12 square feet per mixed gallon because some resin stays in the bucket and some runs over the edges. A 1/16-inch seal coat stretches a gallon to about 25 square feet on sealed surfaces, though bare, porous wood can drink 20 to 30 percent more than the geometric number. The calculator uses the exact geometric volume and lets the waste allowance, defaulted to 10 percent, absorb the real-world losses — so the ounces it reports are what you should actually measure into the mixing cup, not a theoretical minimum you’ll regret at the halfway point of a pour.

Tabletop vs deep-pour epoxy: depth limits are real

Tabletop (coating) epoxy and deep-pour (casting) resin are tuned for different thicknesses, and the calculator’s depth presets follow those limits. Tabletop formulas cure fast and hot: the safe maximum is 1/8 to 1/4 inch per layer. TotalBoat’s TableTop instructions, for example, allow small castings up to 1 inch only if the pour stays under 6 fluid ounces of mixed epoxy, and warn that exceeding 1/4 inch per coat risks excess heat, surface waves, yellowing, or cracking. Deep-pour resins use slower hardeners and accept 2 to 4 inches in a single layer, which is why they’re the right choice for river tables and thick castings. The failure mode when you ignore this is exotherm: epoxy cures through an exothermic reaction, and a thick mass traps its own heat — a neglected full mixing cup can reach 200 to 300°F — which accelerates the cure, which generates more heat. The runaway result is a cracked, clouded, or shrunken casting. If tabletop epoxy is all you own and the project needs depth, pour in 1/4-inch layers at least 3 hours apart; the calculator’s total ounces stay the same, you just split them across layers and days.

What epoxy costs in 2026

As of July 2026, budget $60 to $120 for a 1-gallon kit (resin plus hardener combined) of either type. On the tabletop side, TotalBoat’s Table Top 1-gallon kit sells for about $60 direct and at Home Depot, budget import kits shave that to $40–$50, and premium UV-stabilized bar-top formulas push past $100. Deep-pour pricing lands in the same band: Pour Your Own Epoxy lists its deep-pour fast-cure resin at $60 per gallon, while premium river-table brands such as UltraClear sit near the top of the range (a 1.5-gallon kit runs $159–$169, over $100 per gallon), and per-gallon cost drops noticeably in 3- and 6-gallon kits. That makes volume, not brand, the dominant cost driver. A seal coat plus flood coat on a 2-by-6-foot bar top consumes about 1.5 gallons, or $90 to $180 in material, while a mid-size river table can swallow 2.5 to 3 gallons of deep-pour resin — $150 to $360 before pigment, forms, or finish. Enter your actual kit price in the calculator’s cost-per-gallon field: it multiplies your full volume, waste included, so comparing what a project costs with a $60 kit versus a $110 kit takes seconds instead of a spreadsheet.

A worked river-table example

Say you’re filling a 60-inch river in a coffee-table blank, the void averages 6 inches wide, and the slab is 1.5 inches thick. River mode multiplies 60 × 6 × 1.5 = 540 cubic inches. Divide by 1.805 and the pour needs 299 US fluid ounces of mixed epoxy — about 8.85 liters. Add the default 10 percent waste allowance and the target is 329 ounces, or 2.57 gallons. At a 2:1 mix ratio by volume, that’s 219 ounces of resin and 110 ounces of hardener; at 1:1, an even 165/165 split after rounding. At $80 per gallon for mid-range deep-pour resin, the pour costs about $206 in material before pigment. Two details in this example matter. First, average width does the heavy lifting: measure the river’s width at five or six stations along its length and average them, because live edges taper and the middle is usually the widest point. Second, a 1.5-inch depth sits comfortably inside a deep-pour resin’s 2–4-inch single-layer limit, but the same fill would take six separate 1/4-inch layers with tabletop epoxy — the calculator’s ounces are identical either way, but your schedule is not.

Mixing discipline: volume, weight, and why ratios differ

The calculator splits your total by volume because that’s how consumer epoxies are labeled: 1:1 for most tabletop formulas, 2:1 for most deep-pour resins. If you measure with graduated cups, use those numbers directly. If you measure on a scale — more precise for small batches — do not reuse the volume ratio, because resin and hardener have different densities and the hardener is usually lighter. TotalBoat’s 1:1-by-volume tabletop epoxy, for instance, mixes at roughly 100:83 resin-to-hardener by weight. Every manufacturer publishes the weight ratio on the technical data sheet; use that number, never a converted guess. The other half of discipline is mechanical. Stir for a full 3 to 5 minutes, scraping the sides and bottom of the cup, because unmixed streaks cure soft and sticky. With 2:1 deep-pour resins especially, an off-ratio batch may never fully harden, and there is no fixing it after the pour. Mix only what you can place within the product’s working time — typically 15 to 40 minutes for tabletop epoxy, several hours for deep pour — and never leave a full cup standing, since a concentrated mass builds exotherm heat far faster than the same epoxy spread thin.

Common mistakes that waste resin

The most expensive mistakes happen before anything is mixed. First, underestimating live-edge gaps: a river that’s 4 inches wide at the ends and 9 inches in the middle averages well above 4, and eyeballing the narrow end can leave you 30 to 40 percent short mid-pour. Measure width at several points and enter the average. Second, skipping the seal coat on bare wood: wood holds air, and a flood coat poured straight onto it off-gasses bubbles for hours as the epoxy warms the surface. A thin 1/16-inch seal coat — the calculator’s smallest preset — costs a few ounces and locks that air in. Third, unsealed form seams: deep-pour resin is nearly water-thin and finds every gap in a melamine form, so tape and caulk each joint or your carefully calculated ounces end up on the floor. Fourth, zeroing out the waste allowance: 5 to 10 percent of any batch stays behind as cup residue, stir-stick drips, and edge overflow, which is why the default is 10 percent. Finally, don’t top off with a fresh batch mixed in a dirty cup — cross-contaminated leftovers with stray hardener ratios are the classic cause of permanently sticky spots.