Cost Accuracy Disclaimer
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This page explains exactly how the estimator arrives at a number, so you can judge for yourself how much weight to put on it.
How the calculation works
Every line item is built from four components:
- Materials — area multiplied by a per-unit material rate for the quality tier you pick.
- Consumables — fasteners, adhesives, tape, blades, sealant and similar, as a per-unit rate.
- Labor — area multiplied by typical hours per unit, multiplied by a trade hourly rate.
- Contingency — a 10% buffer added on top of the subtotal.
The total is then presented as a range rather than a single figure, because a single figure implies a precision that no estimate built from typical rates can honestly claim.
Why your real cost will differ
- Region. Labor rates vary widely between metros and rural areas, and between states. The rates here are national-typical, not local.
- Site conditions. Rot, asbestos, knob-and-tube wiring, failed subfloor, out-of-level framing and undersized service all surface after demolition and can move a project substantially.
- Material volatility. Lumber, copper and finished goods move with supply and tariffs.
- Scope creep. The most common cause of overruns is not mispricing, it is deciding mid-project to do more.
- Permits and inspections. Fees, plan review and required upgrades vary by jurisdiction and are not modelled here.
- Contractor demand. The same job is priced differently by a busy firm and a hungry one.
What this tool does not include
- Permit and plan-review fees
- Design, architectural or engineering fees
- Structural work, or repairs discovered after demolition
- Hazardous material testing or abatement (asbestos, lead paint)
- Appliances, furnishings and decor unless you add them as line items
- Sales tax, delivery, dumpster and disposal fees
- Financing costs and temporary accommodation
Use it as a starting point
A good use of this tool is to walk into contractor conversations knowing roughly what the work should cost and what drives the number. A bad use is to commit to a budget or sign a contract based on it. Always get written bids from licensed professionals for your specific property.
Read more about the method in how to estimate a home renovation.