How Much Epoxy Do I Need? (Worked Examples by Project)
The gallons formula with worked examples for countertops, bar tops, cutting boards, river tables and floors — thickness choice, seal + flood coats, waste factor and the kit-rounding trap explained.
Quick answer
Gallons = area × coats × 1.10 waste ÷ coverage rate. Coverage rate comes from your brand's datasheet (TotalBoat: 12.8 sq ft/gal @ 1/8"; Primaloc flood: 16; theoretical 100% solids: 12.8) — or from pure volume for casting: length × width × depth (in³) ÷ 231. Round up to the next kit size, never down. The coverage calculator runs your exact numbers; this page works the examples so you can sanity-check it.
Manufacturer datasheet · 2026-11-07The formula, step by step
- Area. Finished surface in square feet — length × width of the actual top, not the room. Odd shapes: over-measure and trim the plan, not the pour.
- Thickness. The coat you're pouring: 1/16" seal, 1/8" flood (the tabletop standard), 1/4" build. Every datasheet caps a single coat — TotalBoat TableTop at 1/4", ThickSet at 1/2", deep pours at 1.5–3". Respect the cap; heat cracking is not a style.
- Rate. Brand published rate if it exists; otherwise the 1604-rule baseline (1.604 ÷ thickness in inches). Our epoxy brands library lists who publishes what, with sources and dates.
- Waste. ×1.10 — cup residue, sidewalls, drips. Then round up to a real kit.
Worked examples
| Project | Math | Result |
|---|---|---|
| 8×2 ft island top, 1/8" flood, Primaloc (16) | 16 sqft × 1.10 ÷ 16 | 1.10 gal → 2-gal kit |
| Same top, TotalBoat (12.8) | 16 × 1.10 ÷ 12.8 | 1.38 gal → 2-gal kit |
| L-shaped counter 45 sqft, 1/8", theoretical | 45 × 1.10 ÷ 12.83 | 3.86 gal → 4-gal kit |
| Bar top 6×3 ft (18 sqft), seal+flood, TotalBoat | 18 × 1.10 × (1/24 + 1/12.8) | 2.38 gal → 2× 2-gal kits |
| Cutting board 18×12", 1/16" two sides | (1.5 + 1.5) sqft... see note | ≈0.26 gal → 0.5-gal kit |
| River channel 72×8×1.5 in (deep pour) | 864 in³ ÷ 231 | 3.74 gal → 3-gal kit short → 6-gal kit |
| Garage floor 200 sqft, 1/16" roller coat | 200 × 1.10 ÷ 25.66 | 8.57 gal → two 4-gal kits |
Cutting-board note: coating both faces of a 1.5 sq ft board is 3 sq ft of area at 1/16" (25.66 sq ft/gal theoretical) = 0.13 gal × 1.10 waste ≈ 0.14 gal — but kit sizes bottom out at quart kits, so the shelf answers. Small-cast math is why the cost calculator exists: at quart-kit pricing ($180+/gal equivalent), the "cheap" project quietly isn't.
The two mistakes that waste epoxy
Rounding down. Epoxy doesn't pause while you drive to the store. A pour that comes up half a gallon short leaves a visible seam or a half-cured ridge that can't be blended — the job restarts at sand-everything. When your number is within half a kit of the next size, buy the next size; leftovers pour coasters.
Ignoring the seal coat. Bare wood outgasses as the flood coat cures — pinholes and bubbles across the surface, plus a thirsty first flood that soaks in unevenly. A brushed seal coat at roughly half the flood rate costs little and prevents both. Previously painted, sealed or laminated surfaces skip it; raw butcher block never does.
Then the schedule matters more than the volume
Once gallons are settled, the job is timing: recoat inside the datasheet window (TotalBoat: 3 h; Primaloc flood 4–6 h after seal; deep pours 12–36 h depending on the product) so layers chemically bond without sanding, or sand mechanically when the window laps. The brand pages carry every window with its source, and the river table page plans the layer schedule for deep pours.
FAQ
How much epoxy do I need for a countertop?
Measure the finished surface, not the room. A typical 8 ft × 2 ft island top is 16 sq ft; at a 1/8" flood coat with a published rate of 16 sq ft/gal (Primaloc) that's 16 × 1.10 ÷ 16 = 1.1 gallons — a 1-gal kit is short, so buy the 2-gal kit. At TotalBoat's 12.8 rate the same top needs 1.4 gallons. Bare wood adds a seal coat: add ~0.3–0.5 gallons brushed thin.
How much epoxy for a river table?
River tables are volume, not coverage: length × width × depth of the river channel in cubic inches ÷ 231 = gallons. A 6 ft × 8" × 1.5" channel is 72 × 8 × 1.5 = 864 in³ ÷ 231 = 3.7 gallons before waste. Deep pours go in layers (1.5–2" per layer for most resins) — the total doesn't change, but the pour schedule does.
How much epoxy for one coat vs two?
A seal coat (brushed thin, ~1/16") uses roughly half the flood-coat rate per gallon — TotalBoat quotes 24 sq ft/gal sealed vs 12.8 flooded. Plan seal + flood on bare wood: two coats on 40 sq ft ≈ 40 × 1.10 × (1/24 + 1/12.8) ≈ 5.3 gallons at TotalBoat rates. Sealed or previously coated surfaces can usually skip the seal coat.
How accurate is the waste factor?
The 10% default covers cup residue, sidewalls and drips on a careful first pour. Porous raw wood drinks more; perfectly flat sealed molds need almost none. First-timers should treat 10% as a floor — the failure mode of running out mid-pour (a half-cured ridge down the middle of your countertop) costs more than the spare half gallon.
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