Concrete Calculator

Shape

Units

Waste / Overage (%)

Typical: 5–10% (complex forms, rough subgrade → up to 10–15%).

Load from file

“Load from file” accepts a small JSON like {"shape":"slab","unit":"imperial","slab_L":10,"slab_W":12,"slab_T":4}. Nothing is uploaded.

Concrete Calculator – Quick Cheat Sheet

Slab (rectangle): L × W × T. Imperial uses ft & in (T in inches). Metric uses m & cm (T in cm).
Footing/Wall (linear): Length × Width × Depth (width/depth are cross-section). Enter total linear length.
Cylinder/Sonotube: π × (D/2)² × Height.
Waste / Overage: Add 5–10% for spillage, irregular subgrade, and finishing.
Conversions: 27 ft³ = 1 yd³. 1 m³ ≈ 1.308 yd³. 1 ft ≈ 0.3048 m; 1 in ≈ 2.54 cm.
Bag yields (approx): 40 lb ≈ 0.30 ft³, 50 lb ≈ 0.375 ft³, 60 lb ≈ 0.45 ft³, 80 lb ≈ 0.60 ft³.

Notes & edge cases

Footings: If you have multiple wall segments, sum their lengths and enter the total.
Stairs/Irregular slabs: Break into simple shapes (rectangles/cylinders), compute each, then add volumes and reapply waste.
Finish & compaction can change actual yield. Always round your order up to the nearest 0.25–0.5 yd³.