How the epoxy floor calculator works
Epoxy is specified by thickness, not by a spreading rate. A handy identity makes the conversion easy: one litre spread over one square metre forms a layer exactly 1 mm thick. In US units, one gallon spread over 1,604 ft² forms a layer of 1 mil (a thousandth of an inch). The calculator multiplies the floor by the dry thickness and the number of coats, then corrects for solids, because only the solid part of the liquid cures into the coating.
Epoxy (L) = area (m²) × dry thickness (mm) × coats ÷ solids fraction × 1.10In imperial units the same formula divides by 1,604 to turn ft² × mils into gallons. The 10% extra covers porous concrete that absorbs the first coat, resin left in the bucket and roller, and the cove at the wall base.
Worked example
A 6 m × 5 m single garage has 30 m² of floor. A 100% solids system rolled at 0.2 mm per coat, in two coats, needs 30 × 0.2 × 2 = 12 L, or 13.2 L with the allowance. Sold in 5 L kits, that is three kits, and each kit covers 12.5 m² at this build. Change nothing but the product to a water-based epoxy at 50% solids and the same dry thickness needs twice the liquid: 26.4 L. In feet, a 20 ft × 18 ft garage (360 ft²) at 8 mils per coat and two coats needs 360 × 16 ÷ 1,604 = 3.6 gallons, 3.95 with the margin: two 2-gallon kits.
Typical thickness by system
| System | Dry film per coat | Usual use |
|---|---|---|
| Water-based epoxy floor paint | 0.05–0.1 mm (2–4 mils) | Light foot traffic, basements, workshops |
| Solvent-borne epoxy coating | 0.08–0.15 mm (3–6 mils) | Garages with occasional car traffic |
| 100% solids roller coat | 0.2–0.3 mm (8–12 mils) | Daily car traffic, hot-tyre resistance |
| Decorative flake base coat | 0.25–0.4 mm (10–15 mils) | Holds broadcast chips before a clear top coat |
| Self-levelling epoxy screed | 2–3 mm (80–120 mils) | Workshops and commercial floors |
Kits combine resin and hardener; the volume on the label is the mixed total. Garage kits are typically sold in 1-gallon and 2-gallon sizes in North America and in 2.5 L, 5 L and 10 L sets in Europe.
Preparation decides the result
- Profile the concrete. Epoxy sticks to open, sound concrete. Diamond grinding or acid etching removes laitance; a smooth, shiny slab will peel under tyres.
- Check moisture. Tape a 45 cm (18 in) square of plastic sheet to the floor for 24 hours. Dark damp concrete or droplets underneath mean moisture is rising and a standard epoxy will blister.
- Wait for new slabs. Fresh concrete generally needs about 28 days of curing before coating.
- Mind the pot life. Mixed epoxy heats up and hardens in the bucket, often in 20–40 minutes. Pour it onto the floor in a ribbon and spread straight away.
- Add grip where wet. Broadcast anti-slip aggregate into the top coat near doors and ramps, and ventilate well and wear gloves while mixing and rolling.
A reproducible calculation with complete inputs
For a reproducible epoxy floor calculator example, use the metric input system and enter Floor length: 6 m; Floor width: 5 m; Dry film thickness per coat: 0.2 mm; Coats: 2 coats (primer/base + top); Solids content: 100% solids epoxy; Kit size (resin + hardener): 5 L. These settings describe one specific scenario, not a new default for every job. The result follows the method and allowances already explained above. Keep the entire set of values when comparing it with a hand calculation; omitting a selected material or an allowance can change the result even when the dimensions match. The following rows show the unrounded calculation values alongside the precision used by the interface.
| Result | Calculation value | Displayed value | Unit |
|---|---|---|---|
| Epoxy needed | 13.2 | 13.2 | L |
| Kits to buy | 3 | 3 | kits |
| Coverage per kit | 12.5 | 12.5 | m² |
| Floor area | 30 | 30.0 | m² |
How should I prepare these entries?
Floor length: enter the value in m. Floor width: enter the value in m. Dry film thickness per coat: 1 mil = 0.001 in = 0.0254 mm. Roll-on garage coatings: 0.1–0.3 mm (4–12 mils) per coat. Coats: choose among 2 coats (primer/base + top), 1 coat, 3 coats. Solids content: On the technical data sheet. Only the solids stay on the floor; the rest evaporates. Kit size (resin + hardener): enter the value in L. Choose the unit system before transferring your measurements. A depth, length, area and coverage can have different field units even within one system. Read each label individually rather than entering the same unit convention in every box. Optional openings or allowances should describe your actual scenario instead of being silently left at a sample value. The worked inputs above identify exactly which selections produced the table.
Frequently asked questions
How much epoxy do I need for a 2-car garage?
A 2-car garage of about 20 × 20 ft (400 ft²) needs roughly 4.4 gallons of 100% solids epoxy for two coats of 8 mils, including a 10% allowance.
How many square feet does a gallon of epoxy cover?
One gallon covers 1,604 ft² at 1 mil, so about 160 ft² at 10 mils and 200 ft² at 8 mils for a 100% solids product. Water-based epoxy at 50% solids covers half that area at the same dry thickness.
How thick should garage floor epoxy be?
For cars, aim for a total dry film of about 0.3–0.5 mm (12–20 mils) over two or more coats. Thinner paint-type coatings suit foot traffic only.
What does solids content mean for epoxy?
It is the share of the liquid that stays on the floor after curing. A 50% solids product loses half its volume to evaporation, so you must apply twice as much liquid for the same thickness.
Can I apply epoxy on a damp concrete floor?
Standard epoxies should not go on damp slabs or slabs with rising moisture; they blister and delaminate. Test first with a taped plastic sheet and follow the product's moisture limits.