Construction Cost Calculator
Build an itemized new-construction budget from the building geometry, entered unit rates, rooms, trades, fees, overhead and contingency.
| Budget item | Basis | Estimated cost |
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How the construction estimate works
This calculator separates quantities from prices. It derives the footprint, total conditioned floor area, exterior wall area and roof surface from your geometry. It then applies only the unit rates and fixed allowances you enter. That makes it suitable for an early residential or light-building budget without pretending that one national price fits every location or specification.
Geometry formulas: footprint = length × width; conditioned floor area = footprint × stories; net exterior wall area = 2 × (length + width) × wall height × stories × (1 − openings percentage); roof surface = footprint × roof-area factor.
Budget formula: direct subtotal = all quantity-based costs + rooms + fixed trades. Tax = direct subtotal × tax rate. Contractor markup = (direct subtotal + tax) × markup rate. Contingency = (direct subtotal + tax + markup) × contingency rate. Total = direct subtotal + tax + markup + contingency.
Checked example
Example: a 40 × 30 ft footprint with two stories, 9 ft walls, 15% wall openings, a 1.15 roof factor and a 400 ft² garage. Using the default sample rates and allowances, 12% contractor markup and 10% contingency produces a conditioned area of 2,400 ft² and a total of $711,179.39, or $296.32/ft². These prices are illustrative inputs, not market averages.
What to include in your inputs
- Site work: clearing, grading, excavation, drainage or temporary access when those costs are part of the quote.
- Foundation: footings, slab, crawlspace or basement work. Keep basement finishing separate if it is not covered by the shell and interior rates.
- Structure and shell: framing or structural system, sheathing and weather barrier as defined by your estimate.
- Roof and exterior finish: use rates that match the selected assemblies and confirm whether labor, waste, flashing and accessories are included.
- Interior finish: define whether the rate covers insulation, drywall, trim, paint, flooring, doors and cabinetry so costs are not double-counted.
- Rooms and trades: use the kitchen and bathroom fields only for costs not already contained in the interior, plumbing or electrical allowances.
Limits of this calculator
This is an early budgeting tool, not a contractor bid, appraisal, structural design or code review. It does not infer local labor rates, material prices, soil conditions, financing interest, land cost, demolition, escalation, schedule effects, insurance, bond costs, accessibility obligations, environmental remediation or jurisdiction-specific fees. Complex footprints, varying story heights, courtyards and mixed roof forms should be divided into separate takeoffs. Confirm quantities and scope with qualified local professionals before committing funds.