Concrete sealer calculator

The coverage range is the answer, not a footnote

Three sealers, three data sheets, three completely different numbers:

That is a five-fold spread between the extremes. Which product you buy moves the quantity far more than measuring your driveway carefully does, and a calculator that asks for square feet and hands back one number has skipped the only question that mattered.

For a 480 sq ft driveway at two coats on a broom finish, before any waste allowance: 12.8 gallons of penetrating sealer on a thirsty broom finish, or 2.4 gallons of high-gloss acrylic on a smooth, dense one. Same slab, same two coats, and both figures come off a published label.

Texture and porosity are two questions, not one

Every sheet gives the same reason for its range: coverage "will depend on surface texture and porosity". Those are different properties and a slab can have any combination of them — a broom finish that has weathered for ten years is rough and thirsty, while a power-troweled garage floor is smooth and dense. Asking one question cannot separate them, so this page asks two.

Texture is how much surface there is to wet: smooth, broom, exposed aggregate. Porosity is whether the surface will take the sealer at all, and the sheets tell you how to measure it — put drops of water on it. QUIKRETE's own wording: "If the water is absorbed, the surface is porous enough to accept the sealer."

That test has a third outcome, and it is the one worth knowing before you buy anything. If the water beads and sits there, you cannot seal it. All three sheets say not to apply to a non-porous, sealed or painted surface. The answer above goes to zero rather than quoting you a quantity for a job that will peel.

What this page will not do is invent a number between the two published ones. If both indicators say dense, you get the thin end; otherwise you get the thirsty end. It always lands on a figure the manufacturer printed.

That allocation rule is ours, not theirs, and you should know it. The data sheets say only that texture and porosity decide where in the range you land — none of them publishes a table mapping the six combinations of the two onto a rate. We chose to give the thin end only when both indicators agree, which errs toward buying more, because running out mid-slab leaves a lap mark you cannot brush out and a spare gallon costs less than a stripped driveway. If your own label carries a rate for your surface, use that instead.

There is one thing we used to claim here and no longer do: that a second coat spreads further than the first. It is plausible — bare concrete absorbs, a partly sealed surface does not — but no manufacturer publishes a per-coat rate, only a range attributed to the surface. So every coat is costed at the same rate, and if you want to model the difference, halve the coats and run it twice.

Penetrating or film-forming — pick before you price

• Penetrating (silane-siloxane). 7% solids, water-based, non-film-forming. It soaks in and repels water without changing how the slab looks. Nothing to peel, nothing to go white. This is the one for a driveway that sees de-icing salt. It is also the thirstiest.
• Film-forming acrylic. 25% solids, leaves a gloss film, deepens colour on decorative and stamped work. Covers two to four times as far. Its data sheet carries the warning that matters: "Do not apply more than recommended amount." An over-thick acrylic film traps moisture, blushes white and peels, and a third coat is a good way to get there. Two thin coats at right angles, not one heavy one.
• Cure & seal. A dual-purpose product. On fresh concrete it replaces water curing — applied at 200 sq ft/gal to comply with ASTM C309, in two thin layers at right angles, once the surface sheen has gone: typically 4 to 6 hours after placing, as little as 2 to 3 in hot windy weather, 10 to 12 in cool weather. On finished concrete it is a sealer at 150-200 sq ft/gal.

Timing, and the one that catches everybody

New concrete needs 30 days before a sealer goes on it. Both 8800 sheets say so outright. Sealing at a week traps moisture that is still leaving the slab, and on a film-former that shows up as a milky bloom you have to strip.

The exception is a cure & seal, which is designed to go on fresh — that is the whole point of it. If your slab was poured last week, that is your product, not a waterproofing sealer.

Recoat windows differ sharply and are on the label: the penetrating sealer goes on wet-on-wet, a second coat within 5 to 10 minutes, while the gloss acrylic wants 2 hours. Both say the same thing about direction: apply the second coat perpendicular to the first. That is not a finish preference, it is how you avoid a striped slab.

Two more label details worth reading

Both penetrating and gloss products above are water-based, at 33 and 90 g/L VOC, and both state they meet VOC requirements in all locations. Solvent-borne acrylics are still sold and give a wetter look on decorative concrete, but VOC limits vary by state, so check the container against your local rules rather than assuming what a big-box shelf carries is legal where you are.

And a sealer is not a fix for water. The waterproofing sealer's own precautions say not to use it to seal areas prone to standing water, and that it does not replace an exterior membrane on a basement wall. If water is coming up through the slab, sealing the top of it will not stop it.

What the gallon figure assumes about your slab

Three published ranges cover three specific products on one flat, bare, dry surface. Here is where that stops describing the job in front of you:

• Your container may not be one of these three. Epoxy and polyurethane coatings, solvent-borne acrylics and penetrating densifiers are all sold as "concrete sealer" and none of them has a rate on this page. If your label prints a range, use it: gallons is area ÷ that rate × coats.
• Area means flat plan area. Steps, a curb, a rolled edge or the relief in stamped and exposed-aggregate work all carry more surface than their footprint. Picking the textured option moves you to the thirsty end of the range, but it does not measure the extra square footage — for steps, add the riser faces by hand.
• It assumes the whole slab behaves the same way. A driveway that was sealed once, years ago, is usually porous in the traffic lanes and still beading at the edges. One texture and one porosity answer cannot describe that; test several spots and, if they disagree, price the thirsty answer.
• Preparation is not costed here. Stripping an old film, degreasing, etching and pressure washing all come before the first gallon, and a slab that fails the water-drop test needs all of that before the sealer becomes buyable at all.
• Application limits live on the label. Air and slab temperature, humidity, rain and how long the surface must stay dry afterwards decide whether today is the day. Nothing on this page checks the forecast.

The waste allowance covers what stays in a tray, a roller and a short sprayer line. A long hose or a pump you have to prime holds more than that.