Garage Floor Square Footage Calculator

Multiply the interior length by the interior width. A standard two-car garage at 20 × 20 ft is 400 square feet; a 24 × 24 ft build is 576. Subtract anything permanently taking up floor — a water heater platform, built-in cabinets, a stair landing from the house. If you can't get inside to measure, the garage's building footprint from satellite imagery gets you very close, with one adjustment described below.

No, and any tool claiming otherwise is wrong. What you can do is trace the garage's roofline — the building footprint — and use it as a proxy for the floor beneath. Garages are almost always single-story rectangular structures with no setbacks, so the outline of the building corresponds closely to the slab inside it. That's a measurement technique with a known adjustment, not x-ray vision, and it's worth being straight about the difference.

Close, but it reads slightly large, and you should correct for it. The roofline you trace from above includes the eave overhang, which the floor inside does not. A typical residential overhang of 6–12 inches on each side means the traced footprint runs roughly 5–10% above the actual slab. On a 20 × 22 ft garage with 12-inch overhangs, the roofline traces at about 22 × 24 ft — 528 sq ft against a 440 sq ft floor. Subtract 1–2 ft from each dimension for a typical eave, or trace to the wall line where the imagery shows it clearly.

Use the door. Garage doors come in standard widths — a single door is 8 or 9 ft, a double is 15 or 16 ft — and the door is clearly visible in imagery on most properties. Measure the door in the tool and compare it to the standard size; if your door measures 17 ft when it should be 16, everything else you traced is about 6% large and you can correct the whole measurement by that ratio. It's the fastest scale check available on a residential property.

Yes, and better than for garages — those are directly visible from above, so none of the footprint-proxy caveats apply. A carport pad, an open shed floor, an equipment or generator pad, an AC slab, a dumpster pad: trace the concrete itself, the same way you'd trace a driveway. The measurement is direct rather than inferred.

Most fall between 400 and 576 square feet. A 20 × 20 ft garage is 400 sq ft and is the common minimum build; 22 × 22 ft is 484; and 24 × 24 ft, the size that comfortably fits two vehicles plus storage, is 576. Single-car garages usually run 240–336 sq ft, and three-car builds land around 700–800. Older homes tend toward the small end of every one of those ranges.

Concrete cleaning typically runs about $0.25–$0.60 per square foot, which puts a 400 sq ft two-car garage at roughly $100–$240 of work. That's below most contractors' job minimums, which is why real-world garage floor jobs usually land in the $150–$500 range once the minimum, oil-stain degreasing, and any sealing are included. The honest read: garage floors are an add-on, not a standalone trip.

Oil. A driveway is mostly organic soiling that comes off with a surface cleaner and standard chemistry. A garage floor is where vehicles drip for years, so it needs degreasing, dwell time, and often multiple passes on the same stains — with no guarantee that a deep-set stain fully lifts. Add the confined space, water containment inside a building, and the need to move whatever the homeowner has stored in there, and the per-foot rate has to be higher even though the area is smaller.