{"id":"concrete-slab-calculator","name":"Concrete Slab Calculator","shortName":"Concrete Slab","canonicalUrl":"https://calcurhome.com/calculators/concrete-slab-calculator","catalogUrl":"https://calcurhome.com/api/calculators","category":{"id":"concrete-masonry","name":"Concrete & masonry","url":"https://calcurhome.com/calculators/category/concrete-masonry"},"language":"en-US","audience":"US homeowners, DIYers and home-project planners","primaryKeyword":"concrete slab calculator","secondaryKeywords":["slab concrete yards","concrete slab cost calculator","patio slab calculator","garage slab volume"],"description":"Calculate a uniform concrete slab’s cubic yards, surface area, order volume, and material cost from dimensions, waste, and a local per-yard quote.","directAnswer":"A slab’s volume equals its length times width times thickness. Convert thickness from inches to feet and cubic feet to cubic yards, then add placement allowance. This estimate assumes uniform thickness; calculate thickened edges, turn-downs, grade beams, piers, or steps as separate volumes.","inputs":[{"key":"length","label":"Slab length","unit":"ft","defaultValue":24,"min":0.1,"step":0.1},{"key":"width","label":"Slab width","unit":"ft","defaultValue":20,"min":0.1,"step":0.1},{"key":"thickness","label":"Uniform thickness","unit":"in","defaultValue":4,"min":0.5,"step":0.25},{"key":"waste","label":"Placement allowance","unit":"%","defaultValue":7,"min":0,"max":30,"step":1},{"key":"pricePerYard","label":"Concrete price","unit":"$/cu yd","defaultValue":175,"min":0,"step":5,"help":"Enter a local material-only quote."}],"formula":{"title":"Uniform slab volume and concrete subtotal","expression":"Order yards = length × width × (thickness ÷ 12) ÷ 27 × waste factor","explanation":"The calculator converts uniform slab thickness to feet, finds cubic feet, and then converts to cubic yards. The displayed subtotal multiplies order volume by your local per-yard material price only."},"measurementGuide":["Use the slab dimensions shown on approved plans or measured inside finished forms.","Inspect subgrade elevation on a grid so low spots do not silently increase volume.","Separate thickened edges and beams from the uniform field of the slab.","Do not reduce specified thickness to meet a material budget; revise design professionally."],"buyingTips":["Get a written quote covering concrete, delivery, fuel, environmental, short-load, and waiting fees.","Coordinate reinforcement supports, vapor retarder, base, forms, joints, and embedded items before pouring.","Confirm truck or pump access and provide an approved concrete washout location.","Schedule for suitable weather and follow the specified curing method after finishing."],"workedExample":{"title":"Garage-size slab","scenario":"A 24 ft by 20 ft slab is 4 inches thick, with 7% extra and concrete at $175 per yard.","result":"Volume is 5.93 cu yd; order estimate is 6.34 cu yd; material subtotal is about $1,110."},"commonQuestions":[{"question":"How many yards of concrete are in a 20-by-20 slab?","answer":"At four inches thick, a 20-by-20-foot uniform slab contains about 4.94 cubic yards before waste. At six inches, it contains about 7.41 cubic yards. Add thickened edges separately and verify the design thickness."},{"question":"How much does concrete for a slab cost?","answer":"Multiply order-ready cubic yards by a current local ready-mix quote, then add delivery, short-load, pumping, reinforcement, forms, base, finishing, tax, and labor. National averages are less useful than a quote matched to mix and location."},{"question":"Does a slab calculator include footings and thickened edges?","answer":"This calculator covers only the uniform rectangular slab field. Calculate perimeter thickening, grade beams, isolated footings, piers, and steps independently, add their exact volumes, and then apply one placement allowance to the combined order."},{"question":"What thickness should my concrete slab be?","answer":"Thickness depends on intended loads, soil, frost, base preparation, reinforcement, joints, and local building requirements. Common practice is not a substitute for design. Use approved plans or obtain guidance from a qualified engineer or building authority."}],"sources":[{"name":"International Code Council — 2024 International Residential Code","url":"https://codes.iccsafe.org/content/IRC2024P1","note":"Primary model-code source for residential foundations, reinforcement, masonry, and stair safety requirements."},{"name":"Concrete Reinforcing Steel Institute","url":"https://www.crsi.org/reinforcing-basics/","note":"Industry source explaining reinforced-concrete materials and placement fundamentals."}],"defaultCalculation":{"inputs":{"length":24,"width":20,"thickness":4,"waste":7,"pricePerYard":175},"result":{"value":"6.34","unit":"cu yd","label":"Slab concrete to order","lines":[{"label":"Placed slab volume","value":"5.93 cu yd"},{"label":"Slab surface","value":"480 sq ft"},{"label":"Material subtotal","value":"$1,110"},{"label":"Concrete added","value":"0.41 cu yd"}],"summary":"The uniform slab needs 5.93 cubic yards before the selected allowance.","note":"Budget excludes short-load, delivery, pumping, reinforcement, base, forms, finishing, permits, tax, and labor. Verify design with a qualified professional."}},"reviewedOn":"2026-07-23","disclaimer":"Planning estimate only. Verify product coverage, supplier rounding, local codes and structural requirements before purchase or construction."}