This concrete slab cost calculator shows how many cubic yards and bags you need, what the concrete itself costs, and a rough total for a DIY or professionally installed slab. Below you will find the method, current price ranges and real examples such as a 16x20 slab.
How the slab cost is made up
A slab price is more than the concrete. A concrete slab installation cost calculator has to add the compacted gravel base, reinforcement (mesh or rebar), forms, finishing, delivery and labor. That is why the same 4 in slab can cost very different amounts from one town to the next.
Calculating concrete slab cost: the formula
- Cubic feet = length x width x thickness (in) / 12.
- Cubic yards = cubic feet / 27, plus 5 to 10% waste.
- Concrete cost = yards x ready-mix price (plus delivery).
- Add base, reinforcement, forms, finishing and labor, or use a per sq ft installed price.
Concrete slab cost per square foot (2026)
Published numbers vary a lot. A concrete-cost guide puts ready-mix at about $125 to $165 per yard, wire mesh at $0.20 to $0.30 per sq ft and rebar at $2 to $3 per sq ft. Other 2026 guides give about $4 to $8 per sq ft installed for a plain 4 in slab, $6 to $10 for a 6 in slab, and $7 to $14 for reinforced garage slabs. Decorative work costs extra: stamping is often quoted at $10 to $14 more per sq ft. Treat the range as a starting point, not a quote.
Examples: slab cost by size (4 in thick)
| Size | Area | Yards (+10%) | 80 lb bags (+10%) | Concrete only at $150/yd |
|---|---|---|---|---|
| 10 x 10 ft | 100 sq ft | 1.36 | 62 | $204 |
| 12 x 12 ft | 144 sq ft | 1.96 | 88 | $293 |
| 16 x 20 ft | 320 sq ft | 4.35 | 196 | $652 |
| 20 x 20 ft | 400 sq ft | 5.43 | 245 | $815 |
16x20 slab: thickness changes the bill
A 16 x 20 ft slab needs about 3.95 yards at 4 in, 4.94 yards at 5 in and 5.93 yards at 6 in, before waste. At the commonly cited $4 to $8 per sq ft installed, a 320 sq ft slab is roughly $1,300 to $2,600. Read the slab thickness guide before you choose.
Concrete pad cost calculator: small pads
A pad is a small slab, so the same formula applies. A 3 x 3 ft AC pad at 4 in is 3 cubic feet, about 5 bags of 80 lb mix. A 10 x 12 ft shed pad is 1.48 yards, about 67 bags. Small jobs often cost more per sq ft because delivery and setup are spread over less area.
How many yards is one 80 lb bag?
One 80 lb bag yields about 0.60 cubic feet, which is about 0.022 cubic yards, so a yard takes about 45 bags. More in how many bags of concrete in a yard.
What pushes the cost up
- Thicker slabs, rebar and extra base material.
- Poor access, pump trucks and long hauls.
- Demolition and removal of an old slab.
- Decorative finishes. See stamped concrete vs pavers cost.
- Winter work: see pouring concrete in cold weather.
- Permits and inspections where required.
Slab foundation cost
A concrete slab foundation cost calculator like this one gives a budget idea for the concrete and basic costs. A house foundation needs engineered footings, thickness and steel, plus permits, so get a licensed professional involved.
Ways to lower the cost
- Get three itemized quotes for the same size and thickness.
- Use 4 in for patios and walkways when code allows.
- Order the right amount. Use the slab calculator and add only 5 to 10%.
- Compare ready-mix and bags. See the patio concrete guide.
Sources for price ranges
InchCalculator (concrete slab cost, 2026), RemodelAI (concrete slab cost guide, 2026) and other 2026 cost guides. Figures differ by source and region.
Frequently asked questions
How do I calculate the cost of a concrete slab?
Find the volume (length x width x thickness), convert to cubic yards, multiply by the ready-mix price, then add base, reinforcement, forms, finishing and labor. The calculator above does this for you.
How much does a concrete slab cost per square foot?
Sources commonly cite roughly $4 to $8 per sq ft installed for a plain 4 in slab, with higher figures ($7 to $14) for reinforced garage slabs. Local labor and site conditions change this a lot, so get quotes.
How much does a 16x20 concrete slab cost?
A 16x20 ft slab is 320 sq ft. At the commonly cited $4 to $8 per sq ft that is roughly $1,300 to $2,600, and concrete alone is about $650 at an example $150 per yard.
Is a concrete pad cheaper than a slab?
A pad is just a small slab, so the method is the same. Small jobs often cost more per sq ft because delivery and setup are spread over less area.
Does the calculator work for a slab foundation?
It gives a budget estimate for the concrete and basic slab costs. A house foundation needs engineered footings, thickness and steel, so ask a licensed professional and your building department.