Concrete Slab Calculator
Enter dimensions and instantly compare yards, bags, truck delivery, reinforcement and cost.
1.36 yd³ concrete needed
$90 short-load surcharge included.
62 bags is a substantial hand-mixing job.
Full material breakdown62 bags · $330 truck
Method & worked exampleHow this estimate works
Open guide
10 × 10 ft patio, fully unpacked
A 10 × 10 ft patio at 4 inches uses 33.3 ft³, or 1.24 yd³ net. With 10% waste, plan for 1.36 yd³: 62 × 80 lb bags. A truck order rounds to 1.5 yd³. A 16-inch rebar grid would use about 160 lineal feet, or 8 × 20-ft bars.
Four steps from dimensions to order
- Enter the length and width of your slab.
- Set the thickness, or tap a project preset such as patio, driveway, or garage.
- Choose reinforcement, gravel depth, and a waste factor.
- Read the cubic yards, bag counts, truck order, and cost; drag the 3D slab to inspect it.
Transparent assumptions
Volume = length × width × (thickness ÷ 12) in cubic feet; divide by 27 for cubic yards. Bags use yields of 0.30 / 0.375 / 0.45 / 0.60 ft³ for 40 / 50 / 60 / 80 lb and always round up.
We add your waste factor, then round a ready-mix order up to the next quarter yard. Truck pricing uses at least a one-yard invoice and includes your short-load surcharge below a full load. Normal concrete is estimated at 150 lb/ft³.
Practical answers
Concrete calculator FAQ
How much concrete do I need for a 10 × 10 slab?
At 4 inches thick, a 10 × 10 ft slab uses about 1.24 cubic yards net, or 1.36 cubic yards with 10% waste. That is 62 × 80 lb bags. A ready-mix order rounds up to 1.5 cubic yards.
How many bags of concrete are in a cubic yard?
One cubic yard is about 45 × 80 lb bags, 60 × 60 lb bags, 72 × 50 lb bags, or 90 × 40 lb bags. Always confirm the yield printed on the product you buy.
Should I use bags or ready-mix?
Under about 1 cubic yard, bags are often practical. Over 2–3 cubic yards, ready-mix usually saves substantial labor. Small truck deliveries may carry a minimum order and a short-load surcharge, both included in this estimate.
How thick should a concrete slab be?
A common starting point is 4 inches for patios, walkways, and sheds; 5 inches for car driveways; and 6 inches for heavier vehicles or garages. Soil, load, frost depth, and local code govern the final design.
What rebar do I need?
Light 4-inch slabs often use 6 × 6 wire mesh or #3 bar. Vehicle slabs commonly use #4 bar at 12–18 inches on center. These are estimating defaults, not structural design; local code and an engineer govern.
How much does concrete weigh and cost?
Normal concrete weighs about 150 lb per cubic foot, roughly two tons per cubic yard. Ready-mix commonly runs around $140–185 per yard before local delivery charges. Every price in the calculator is editable.
Do you store my measurements?
Calculations run in your browser and this site uses no account, analytics, or advertising cookies. Your last inputs may be stored locally on your device. If you open or share a generated link, its measurement parameters are included in that URL.