A garage floor looks like the easiest job on the board: a rectangle, indoors, out of the weather. It prices higher than that reads, because it lives under vehicles and it has to hit grade against a foundation that is already there. Quote it as a garage, not as a big patio.
Why it is not patio flatwork
Two things separate a garage floor from an open patio pour of the same size, and both cost money.
Thickness. Wheel loads want 5 to 6 inches where a patio takes 4. Going from 4 to 6 inches is half again as much concrete in the same footprint, so if you carry one flat slab rate it quietly loses money on every garage. The load case is spelled out in 4 inch vs 6 inch slab.
Reinforcement. Rebar or mesh is cheap insurance under cars. At the example rate of $1.50 per square foot it adds $726 on a 484 square foot two-car floor. That is a line the customer should see, because it buys crack control they will notice for twenty years.
Rate, worked out
Start with square footage times your finish rate. Garages almost always get a plain broom finish, so the example $9 per square foot is the usual base: a 22 by 22 two-car floor at 484 square feet is about $4,356 before add-ons. Those are example rates only; your mix cost and market set the real number. The finish upcharge matters less here than on a pool deck, so the money is in the prep and the reinforcement, not the surface.
Tear-out and grade are the real work
Most garage floors are replacements, which means demolition first. Tear-out at the example $4 per square foot is $1,936 on that 484 foot floor, and it belongs on the quote as its own line so the customer sees what the demo buys. Then the pour has to meet the foundation cleanly, clear the door openings, and slope toward the door so water runs out instead of standing. That is careful work, and it is why an indoor rectangle is not a quick number.
Run your own footage on the garage floor concrete calculator, or see it worked at a common size on the 22x22 garage floor cost page. The general method behind any flatwork number is in how to price a concrete slab. Put your real rates into PriceDesk and every garage floor quotes itself from your phone in about ten seconds. Free for 14 days, no card.