Construction calculators
Quantities, labor and equipment hours, cost, bids, change orders and retainage.
Calculate rebar quantity step by step: Bars each way = floor(clear span ÷ spacing) + 1.
Calculate asphalt quantity step by step: Tonnes = length × width × thickness × compacted density × (1 + waste).
Calculate excavation step by step: V = D ÷ 6 × (A_bottom + 4·A_mid + A_top) (prismoidal formula).
Calculate backfill step by step: Compacted fill = excavated − structure volume.
Calculate masonry step by step: Units/m² = 1 ÷ [(L + joint) × (H + joint)].
Calculate drywall step by step: Sheets = ⌈(perimeter × height + ceiling − openings) × (1 + waste) ÷ sheet area⌉.
Calculate framing step by step: Common studs = floor(length ÷ spacing) + 1.
Calculate labor hours step by step: Crew hours = quantity ÷ (production rate × efficiency).
Calculate equipment hours step by step: Machine hours = quantity ÷ (output × working minutes ÷ 60).
Calculate construction cost step by step: Direct = material qty × unit price + labor h × rate + equipment h × rate + subcontractor.
Calculate contractor bid step by step: Bid = (direct + overhead + contingency) × (1 + markup), or ÷ (1 − margin).
Calculate subcontractor quote step by step: Levelled quote = quote + excluded items.
Calculate change order step by step: Net = added − deleted.
Calculate retainage step by step: Earned = contract × % complete.