Construction & DIY Calculators

How the concrete & gravel calculators work

Bulk materials are sold by volume — cubic yards for ready-mix and gravel, cubic feet for bagged mix. For a rectangular slab, footing, gravel bed or garden bed, volume is length × width × depth (with depth converted from inches to feet). For a round column we use π × radius² × height. Divide cubic feet by 27 for cubic yards, then by the bag yield to get bag counts. Gravel weight assumes roughly 1.4 US tons per cubic yard, a typical figure for crushed stone.

Roofing and drywall

Roofers measure in squares (100 ft²). We take your building footprint, multiply by a pitch factor to account for the slope, and divide by 100. Drywall is estimated by dividing total wall and ceiling area by the sheet size, then adding waste for cuts around doors and windows.

Tip: always round up

Running short mid-job means a delay or a weak joint. A 10% waste allowance is standard; bump it to 15% for uneven ground, complex cuts or hand-mixing.

More tools: Square Footage Calculator — measure any room, floor or plot and estimate material cost.