How many cubic yards of concrete do I need?

Volume is slab area times thickness, converted to cubic yards and increased by a waste factor for subgrade variation and spillage.

Do I need rebar or wire mesh?

Reinforcement choice depends on slab thickness and load. The takeoff generates a rebar grid or mesh sheet count from your spacing, plus chairs to hold it mid-slab.

How far apart should control joints be?

A common guide is joint spacing in feet no greater than two to three times the slab thickness in inches. Your plan lists the spacing used in the estimate.

Are the material costs accurate for my area?

Costs are regional estimates only, indexed by ZIP against national material averages. Always confirm current prices with your supplier before buying — the numbers here are for planning and budgeting, not a quote.

Do I need to confirm my measurements first?

Yes. The calculator asks you to verify key dimensions before it will produce material, cut, or shopping lists, because a single mistyped dimension changes every quantity downstream.

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Concrete slab · Step 1 of 5 · Slab size

How big is the pad?

10×12 fits a small patio table + 4 chairs. 12×16 fits a full dining set. Anything over 400 sq ft is a serious pour — call a pro or line up 4-5 friends.

Length

Width

Live estimate

Prices for your area

Enter your ZIP to re-price materials, or keep national averages.

Reviewed weekly · price book updated 2026-07-27See what changed

DIY vs. hiring a pro

Free

Save about $1,139 (65%)

building this concrete slab yourself.

You build it$616

Materials only, your sweat.

A contractor builds it$1,755

Typical bids land $1,544–$2,071.

Materials: $770
Labor: $985
Est. hours: 18

Contractor figures assume a $55/hr blended labor rate (national average). Estimates only — use them to sanity-check a bid, not as a quote.

Cut-list optimizer

Free

Buy 23 boards · 9% offcut

276 linear ft purchased, 252 ft used — 24 ft ($14) left over.

19 × #4 @ 12'
Rebar – long runs, Rebar – short runs · 1 piece per board
20 ft scrap (9%)
4 × 2 × 4 @ 12'
Forms – long sides, Forms – short sides · 1 piece per board
4 ft scrap (8%)

Estimates only. Includes a 1/8" blade kerf per cut. Measure your own site and check board lengths at the yard before buying.

Slab thickness4" vs 4" min (general use)
4" thickness meets typical residential patio/walkway guidance.
Slab rebar spacing16" vs 24" max spacing
16" rebar grid spacing is within typical residential guidance.

This is an automated sanity check against published residential span guidance — estimates only, not a stamped engineering review. Local code and your inspector always govern; confirm sizing and embedment with your building department before you build.

Check a contractor bid

Free

Enter what a pro quoted you. We'll break it down against this project's materials and national labor rates.

Bid totalMaterials (optional)Labor (optional)

$616

incl. 10% waste

Materials

Area: 120 sqft
Concrete: 1.48 cu yd
Gravel: 1.48 cu yd
Rebar: 208 ft

Concrete slab calculator questions

Common questions about this takeoff. All output is an estimate only — confirm quantities and prices before you buy.