How Much Floor Does a 55-Gallon Drum of Epoxy Cover? Drum Sets, Fill Volumes and Bulk Pricing

Once a project gets past a couple of garage bays, people start asking about drums. The thinking makes sense: if a 3-gallon kit covers a garage, a 55-gallon drum should cover a warehouse for less money. Then the questions start. Why can't I buy just one drum? Why does the drum say 50 gallons when it's a 55-gallon drum? Is bulk actually cheaper once everything is counted? This guide covers the coverage math first, then how drums are sold, then whether bulk makes sense for your job.

How many square feet a drum covers

Coverage depends on the film thickness you're applying, not the container. The math for 100% solids epoxy is simple. One gallon spread over 1,604 square feet leaves a film one mil thick (a mil is a thousandth of an inch). Divide 1,604 by the thickness you want and you have square feet per gallon.

• 8 mils: about 200 sq ft per gallon
• 10 mils: about 160 sq ft per gallon
• 12 mils: about 134 sq ft per gallon
• 16 mils: about 100 sq ft per gallon

For a typical 10-mil floor coat, 50 gallons of mixed material covers roughly 8,000 square feet. That's the number to start with, but it isn't the number to order from.

Real floors use more than the math says. Porous or freshly ground concrete soaks up the first coat. Low spots, pits and saw cuts take extra. Some material stays in buckets, rollers and squeegees. Plan on 10 to 15 percent extra on a smooth, well-prepped slab and 20 percent or more on rough or very absorbent concrete. A broadcast flake or quartz system also needs enough material to lock the aggregate in place, so check the spread rate for the specific coat you're applying.

If you want this to apply to more than epoxy, note that it only holds for 100% solids products. Water-based and solvent-based coatings lose volume as they cure, so they cover more square feet wet but leave a thinner film. Our guide on what 100% solids epoxy means explains why that matters.

Why 2:1 epoxy comes as a three-drum set

Floor epoxy is two components: resin (Part A) and hardener (Part B). They only cure correctly at the ratio they were formulated for. With a 2:1 product, every gallon of mixed epoxy is two parts resin to one part hardener.

Since drums are filled to the same volume, the only way to package a 2:1 ratio in drums is two drums of resin and one drum of hardener. Selling one drum on its own means selling resin with no hardener, or hardener with nothing to cure. Neither does anything on a floor. That's why 2:1 flooring epoxy in drum quantities is sold as a three-drum set.

It also means the coverage numbers above apply to the whole set, not each drum. If each drum holds 50 gallons, a three-drum set gives you 150 gallons of mixed epoxy. At 10 mils, that's roughly 24,000 square feet of single-coat coverage before waste, or about 12,000 square feet if you're applying two coats.

Other ratios package differently. A 1:1 product would come as a two-drum set. In every case, plan on buying the full matched set.

Is a 55-gallon drum really filled to 55 gallons?

Usually not, and that's intentional. A 55-gallon drum is the container size. Manufacturers typically fill it to around 50 gallons and leave headspace. Resin expands and contracts with temperature during shipping and storage, and a drum filled to the brim can bulge, leak or spit when opened. The headspace also leaves room to mix or stir inside the drum.

So when you see a drum listed as 50 gallons, that's the net volume of product, and it's the number to use in your coverage math. Always check the stated net contents rather than going by the drum size. If you've done your coverage math based on 55 gallons per drum, you'll come up about 9 percent short.

Are drums cheaper than 3-gallon kits?

Per gallon, bulk material usually costs less. Whether the job ends up cheaper is a different question. Here's what to factor in before you switch.

• Freight: A three-drum set of epoxy weighs well over a thousand pounds and ships by freight truck on a pallet. You need a dock or a forklift, or you need to pay extra for liftgate delivery. That can wipe out the per-gallon savings on a mid-size job.
• Dispensing equipment: You can't tip a drum into a bucket. You'll need drum pumps for each component and an accurate way to measure the ratio for every batch. Small kits are pre-measured. With drums, getting the ratio right is your job, and an off-ratio batch leaves soft, tacky or blotchy spots that have to be ground out.
• Leftover material: Open drums need to be resealed and stored at stable temperatures. Epoxy resin that sits cold can crystallize and has to be warmed before use. If you won't use most of the set within its shelf life, the leftover is money spent on nothing.
• Crew size and pot life: Bulk only pays off if you can mix and place large volumes quickly. Mixed epoxy has a limited working time, so drums suit crews that can run batches back to back across a big open slab.

A rough rule: for a residential garage or basement, kits almost always make more sense. They're pre-measured, ship by parcel and leave little waste. Drums start to make sense on commercial and industrial floors in the tens of thousands of square feet, or for contractors running several jobs with the same product. If your total job, primer through topcoat, uses most of a three-drum set within a few months, ask about bulk. If it doesn't, stick with kits. Our guide to commercial epoxy flooring cost goes deeper on large-job budgeting.

Don't forget the rest of the system

Drum math usually focuses on the body coat, but a floor system includes more layers. You may also need a primer, crack and joint filler, flake or quartz broadcast, and a topcoat such as polyaspartic or polyurethane. Each has its own spread rate and may come in different containers. Run each coat separately so you don't end up with plenty of base coat and not enough topcoat.

What we recommend

Start with square footage and the system you want, not the container. Our epoxy calculator works out quantities per coat, including waste. For garages, basements and shops up to a few thousand square feet, the kit builder puts together pre-measured kits for each layer so nothing is mixed off-ratio. To compare build-ups before ordering, see our epoxy floor systems. Contractors and facilities planning large floors can find bulk options and pricing on our pros page.

FAQ

Can I buy just the resin drum and use a hardener from another brand?
No. Resins and hardeners are formulated as a pair. Mixing brands, or even different products from the same brand, can lead to poor curing, weak adhesion or discoloration, and voids any product support. Buy the matched set.

How long does a drum set keep once it's opened?
Sealed tightly and stored indoors at moderate temperatures, unmixed components typically keep for many months. Check the shelf life on the product data sheet. Keep drums off cold floors, reseal right after dispensing, and warm resin gently if it has crystallized.

Is a three-drum set enough for my floor?
Multiply your square footage by the number of coats, divide by the spread rate for your thickness, and add 10 to 20 percent for waste. At 10 mils, 150 gallons of mixed epoxy covers about 24,000 square feet in one coat. More answers are on our FAQ page.