Concrete Calculator
Estimate how much concrete your project needs before ordering. Enter length, width and depth to calculate cubic yards plus an approximate 80 lb bag count.
Concrete slab, pad or general flatwork
See the project dimensions, concrete thickness, compacted gravel base, form-board length and stake spacing, plus reinforcement, vapor-barrier, control-joint, curing and waste inputs used by the full concrete planner.
Start with the essentials
Enter the pour dimensions first. Waste and purchase assumptions stay available below.
CUSTOMIZE PROJECT DETAILSAdjust assumptions & product details+
Check the method or common questions
Method, formula & assumptions
Concrete estimating basics
Formula: Volume = length × width × thickness. PlanDIYBuild converts thickness from inches to feet, then converts cubic feet to cubic yards. Bag estimates use the stated approximate yield for each common bag size.
Worked example: Example: a 10 × 12 ft slab at 4 in thick has 40 ft³ of geometric volume before extra material. Divide cubic feet by 27 to convert to cubic yards.
Before you buy: Concrete projects commonly need extra material for grade variation, spillage and imperfect measurements. Use the adjustable extra-material percentage and confirm the yield printed on the mix you plan to buy.
Concrete Calculator FAQ
Should I order exactly the calculated amount?
Usually no. Real forms, subgrade and measurements are rarely perfect. The calculator lets you add extra material so you can plan above the geometric minimum.
Are concrete bag yields exact?
No. Bag yield varies by product. Treat the displayed bag counts as planning estimates and verify the yield printed on the specific mix before buying.
Continue your Concrete project
Use the Concrete planning hub for related calculators and quick-reference guides.
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