The Concrete Calculator estimates mixed volume for slabs, cylinders or a known area with depth. Combine up to 10 regions, add a material allowance and convert volume to cubic feet, cubic yards and cubic metres. Whole bags use the mixed yield you enter; optional prices add a material budget.
Use it for uniform slabs or complete cylindrical pours. Cylinder mode uses diameter and depth. For a post hole already occupied by a post, supply a separately measured net area: the tool does not infer an annular gap. Measure footprints with square footage, or estimate aggregate with gravel.
US inputs use feet for lengths and diameter, inches for depth, and square feet for known area. Metric inputs use metres, centimetres and square metres respectively. Active dimensions must be positive, at most 1e12. Allowance is 0–100%. Enter the bag’s mixed yield in ft³, litres or m³. Prices are optional, non-negative and use one selected currency label.
Rectangle area = length×width. Circle area = π×(diameter/2)². Base volume = sum of area×depth. Adjusted volume = base×(1+allowance/100). Bags = ceiling(adjusted volume/bag yield). Unit factors: 1 ft = 0.3048 m; 1 in = 0.0254 m; 1 ft³ = 0.028316846592 m³; 1 yd³ = 0.764554857984 m³.
A 12 ft×10 ft slab at 4 in thick has volume 12×10×(4/12)=40 ft³, about 1.481481 yd³ or 1.132674 m³. With no allowance and an illustrative mixed yield of 0.6 ft³ per bag, 40/0.6=66.666667, so buy 67 whole bags. At an example 8 currency units per bag the material cost is 536; this is not a market quote.
使用產品標註的混合後體積，不用包裝重量換算。示例每袋 0.6 ft³，可按產品資料修改。
先增加餘量再向上取整袋數；袋裝成本使用整袋數，散裝成本使用未取整體積。
僅估算材料，不計算結構設計、配筋、強度、人工、配送或稅費。單位切換換算有效尺寸與散裝價格口徑；幣種不做匯率換算。
從尺寸算到成品體積與購買袋數。