At 20x24 you are looking at 480 square feet, the standard two-car garage slab. Of every size on this list, this is the one where thickness talk matters most, because this exact footprint gets poured for garages every day of the week.
The base example math
| Finish | Example rate | 20x24 (480 sq ft) |
|---|---|---|
| Standard broom | $9 / sq ft | $4,320 |
| Stamped | $16 / sq ft | $7,680 |
Example rates, clearly. A garage floor gets broom finish; the stamped row is what this footprint costs as a patio at the example rate, and the $3,360 gap between the rows is the finish decision made visible.
The two inches nobody can see
A 4 inch slab and a 6 inch slab look identical the day after the pour. The difference is underneath: 480 square feet at 4 inches is about 6 yards of concrete (480 x 1/3 divided by 27), and at 6 inches it is about 9 yards. Half again the material, hidden in the ground, carrying every wheel load for the next thirty years. For a slab that parks two vehicles, that is not the place to economize, and 4 inch vs 6 inch slab walks the whole trade-off.
Reinforcement rides along with the same logic. At the example add-on of $1.50 per square foot, mesh across this slab is $720.
Where the rest of the money hides
Replacing an old garage floor means demo first: at the example $4 per square foot, tear-out on 480 square feet is $1,920, nearly half the base broom number again. Site prep and grading at the example $2 adds $960. A quote that itemizes those lines wins against a mystery lump sum, because the customer can see what the money does.
Check the math on any size
Your market’s broom rate is not $9, it is whatever your costs and margin say it is. What to charge per square foot for flatwork shows how to build that number, and the concrete slab cost calculator runs any footprint against the example rates.
Load your real rates into PriceDesk once and this quote, thickness call and all, is a ten-second job from the cab. Free 14-day trial, no card.