Skip to content
Blueprint Calc

Concrete Slab Calculator

Pour a slab — patio, shed floor, garage, driveway. Enter dimensions and thickness, get concrete yards, bag count, and a sanity check on whether a ready-mix truck is cheaper.

How much concrete for a slab?

Default: 10x10 ft patio at 4 in thick.

You need
  • Concrete volume
    1.36 cu yd
    33.33 cu ft + 10% waste
  • 60 lb bags
    82 bags
    60 lb bag yields 0.45 cu ft
  • Ready-mix truck
    Order 2.00 cu yd
    Most suppliers require a 3 cu yd minimum. Below that, expect a $50-200 short-load fee — or ask for a volumetric (mobile-mix) truck which delivers as little as 0.5 yd.

What you'll need to buy

Prices approximate · Links go to retailer search results
Estimated total: ~$482 (materials, before tax)

Product links go to Home Depot search results — pick the best match for your project. Prices shown are rough averages.

How we calculated it

Concrete slab volume uses the basic box formula:

Volume (cu ft) = length (ft) × width (ft) × (thickness (in) ÷ 12)

For a standard 4" patio slab, that is area × 0.333. Divide cubic feet by 27 to get cubic yards. Then:

  • 60 lb bags = cu ft ÷ 0.45 (yield per bag)
  • 80 lb bags = cu ft ÷ 0.60
  • Ready-mix truck threshold: 1 cu yd minimum order, worth it above 1.5 yd

Slab thickness rules of thumb: 4" for patios, sidewalks, shed floors. 6" for driveways and garage floors. Always include reinforcement — #4 rebar on 16-24" centers or 6x6 wire mesh mid-depth. Under a 4" slab, a 2" bed of compacted gravel drains water and prevents frost heave.

Frequently asked questions

How much concrete do I need for a 10x10 slab?
A 10x10 slab at 4" thick = 100 × 0.333 = 33.3 cubic feet, or about 1.23 cubic yards with 10% waste. That is roughly 56 × 60 lb bags or 42 × 80 lb bags. 1.23 yards is below most suppliers' 3 cu yd minimum, so a ready-mix truck for a slab this size usually involves a $50-200 short-load fee — or a volumetric / mobile-mix truck that pours on demand.
How thick should a concrete slab be?
4" minimum for patios, sheds, and walkways. 6" for driveways and garage floors. 8"+ for heavy equipment pads. Thinner than 4" cracks under normal residential loads. Always use rebar or wire mesh reinforcement.
Do I need rebar in a concrete slab?
Yes, for anything larger than a stepping stone. Either 6x6 wire mesh laid mid-depth or #4 (1/2") rebar on a 16-24" grid. Reinforcement does not stop cracking — it holds cracks tight when they happen.
How many 80 lb bags of concrete per yard?
One 80 lb bag of Quikrete yields 0.60 cubic feet. At 27 cubic feet per yard, you need 45 bags of 80 lb to make one yard. That is ~3,600 lbs of mixing — which is why most people switch to a ready-mix truck above 2-3 cubic yards.
When should I use bags vs a ready-mix truck?
Under 0.5 cubic yards (about a dozen 80 lb bags): bags. 0.5-2 yards: bags still workable but painful; ready-mix suppliers usually charge a $50-200 short-load fee below their 3 cu yd minimum, or a volumetric / mobile-mix truck can deliver as little as 0.5 yd. Above 3 yards: call for a standard ready-mix truck — cheaper per yard than bags and way faster.
How long does concrete take to cure?
Initial set: 24-48 hours (walkable). Usable for light loads: 7 days (~70% strength). Full design strength: 28 days. Driveways should not see vehicles for at least 7 days. Keep concrete damp for the first week — faster drying = weaker finish.
Can I pour concrete in cold weather?
Down to 40°F is workable with hot water in the mix and insulating blankets. Below 40°F, concrete stops curing and can freeze before it sets, ruining the pour. Most ready-mix suppliers add a cold-weather admixture in winter.
How much does a concrete slab cost?
Materials only: about $5-7 per sq ft for a 4" slab (concrete + rebar + base gravel). With labor for a professional pour: $8-18 per sq ft typical, higher in urban markets. DIY saves the labor but costs your weekend and some back pain.

Other calculators

Paint calculator
Gallons of paint and primer for any room.
Drywall calculator
Full material list for any room.
Tile calculator
Tile count, boxes, thinset, grout, spacers.
Mulch calculator
Yards, bags, and bulk delivery estimate.