Concrete Slab Cost Calculator: DIY vs Hiring a Pro by Size
Updated · See the full concrete slab installation cost comparison
Shed pad to 30×30 shop: DIY from $875 in mix and rentals, a finisher from $700.
- Pick the size closest to yours; every figure is for a 4-inch slab. For an in-between size, scale by area — a 16×20 (320 sq ft) is about 80% of the 20×20 numbers.
- On the DIY tab, the 20×20 and 30×30 include a skid steer rental for the dig and a plate compactor; the 30×30 adds a line pump. Untick what you'd do by hand or borrow, and put a real number on your hours.
- On the Hire a pro tab, tick a 6-inch slab and rebar for anything with wheels on it, and a thickened edge or footing if a building goes on top — together they add $1,400–$5,500 to a 20×20 and are what separates a patio quote from a garage quote.
- DIY comes out ahead at all four sizes, but only by about $100 on a 10×10 or 12×12. If you'd have to buy the wheelbarrow too, that margin is gone.
Calculate cost
| Tools to buy or rent | $552 |
|---|---|
| Materials | $1,792 |
| Disposal | $112 |
| DIY cash cost | $2,456 |
| Your time (32 h × $25) | $800 |
| DIY all-in | $3,256 |
DIY saves about $344 after valuing your time ($1,144 in cash).
National estimates for planning. Doesn't include the risk-side costs described on the comparison page.
Typical results by job size
Defaults the calculator starts from: commonly owned tools excluded, typical pro price, no add-ons.
| Size | Verdict | DIY | Pro | Your hours | Typical savings | Break-even |
|---|---|---|---|---|---|---|
| 10×10 shed or hot-tub pad | DIY | $875–$1,105 | $700–$1,500 | 10–16 hours | $110 (10%) | $8/hour |
| 12×12 patio | DIY | $1,115–$1,373 | $900–$1,800 | 12–20 hours | $106 (8%) | $7/hour |
| 20×20 garage or parking pad | Hire | $2,344–$2,718 | $2,400–$4,800 | 24–40 hours | $1,069 (30%) | $33/hour |
| 30×30 workshop or barn slab | Hire | $5,380–$5,994 | $5,400–$10,000 | 45–70 hours | $2,013 (26%) | $35/hour |
Break-even is what an hour of your time would have to be worth for DIY and hiring to cost the same. Above it, hiring is cheaper all-in. See how these are calculated.
Reading the result
The size you pick applies to both tabs, and everything is for a 4-inch slab.
Do it yourself totals concrete, gravel, form lumber, reinforcement and curing materials scaled to the size, plus the rentals that size needs — a mixer for bagged mix on the small slabs, a skid steer and plate compactor on the large ones, a pump on the 30×30 — plus the finishing tools you don’t own, plus your time at whatever rate you set. Hours are your own: 10–16 for a 10×10, 24–40 for a 20×20, 45–70 for a 30×30, and they don’t include the two to four helpers a ready-mix pour needs.
Hire a pro starts from a low, typical or high installed price for that size, then adds what a base quote leaves out: a 6-inch slab for vehicles, a rebar grid, a thickened edge or footing for a building, a pump where a truck can’t reach, extra excavation on a slope, removing an old slab, a decorative finish, and the permit. Tick what your job needs and compare to your DIY total.
What neither tab includes: the cost of a pour that goes wrong. A truck that arrives before the forms are ready, an order that comes up a yard short, or a surface that set before it was floated isn’t a line item — it’s a second slab. The cost comparison is honest about which sizes that risk is worth, and the DIY guide is about the ones where it is.
Frequently asked questions
How do I figure out how much concrete my slab needs?
Length × width × thickness, all in feet, divided by 27, plus 10% for uneven excavation. A 4-inch slab is 0.333 feet thick, so a 20×20 is 20 × 20 × 0.333 ÷ 27 = 4.9 cubic yards — order 5.5. A 10×10 is 1.23 yards, or about 56 bags of 80 lb mix (each yields 0.6 cubic feet). For a thickened edge, add the perimeter length × edge width × extra depth separately.
Why does the 20×20 DIY estimate include a skid steer rental?
Because 400 square feet dug 8 inches deep is about ten cubic yards of soil — a hundred wheelbarrow loads — and a rented skid steer or mini excavator does it in a day for about $300 plus delivery. Untick it if you're willing to spend two or three days with a shovel, or if the site is already at grade. The plate compactor is separate: the base still has to be compacted, and a hand tamper isn't enough for 400 square feet.
What do the quote levels mean for a concrete slab?
Low is a plain 4-inch broom-finished slab on an easy, flat site in an inexpensive market, or a small contractor between bigger jobs. Typical is the national median for that size with a compacted base, mesh and a standard finish. High is a difficult site — slope, poor soil, long wheelbarrow runs — or a coastal metro, or a crew that only does premium flatwork. The add-ons are separate from the level: thickness, rebar, footings, a pump and finishes are priced on top of whichever level you choose.
Sources
- Cement Masons and Concrete Finishers (SOC 47-2051), Occupational Employment and Wage Statistics , U.S. Bureau of Labor Statistics, 2026-04
- How Much Does a Concrete Slab Cost? , HomeGuide, 2026-09
- How Much Does a New Concrete Slab Cost? , Angi, 2026-09
- How Much Does a Concrete Slab Cost? , HomeAdvisor, 2026-09
- Concrete Volume Calculator , Quikrete, 2026-09
- International Residential Code, Chapter 5: Floors (R506, Concrete Floors on Ground) , International Code Council, 2026-09
- Concrete mix, rebar, mesh and form lumber pricing , The Home Depot, 2026-09
Figures last reviewed . See how we estimate.