Construction Cost per Square Foot Calculator
Estimate build cost from area and rate, with contingency and soft costs.
Please note: Estimates only, not investment or legal advice. Property markets, taxes, fees and lending rules vary by location and change over time. Verify figures with a qualified professional before committing.
What the Construction Cost per Square Foot Calculator does
A build budget is more than area times rate. Soft costs for design and permits, site works, and a contingency for the overruns that construction reliably produces all sit on top of the headline construction figure.
Formula
Hard cost = Floor area × Cost per unit areaSoft costs = Hard cost × Soft cost percentageContingency = (Hard + Soft + Site works) × Contingency percentageTotal = Hard + Soft + Site works + Contingency + Land
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Floor area | number | Yes | Accepts 1 or more. |
| Area unit | one of 2 options | Yes | — |
| Cost per unit area | selected currency | Yes | Per square foot or square metre, matching your selection. Accepts more than 0. |
| Contingency | % | Yes | Buffer for overruns — 10-15% is typical. |
| Soft costs | % | Yes | Design, permits, engineering, project management. |
| Land cost | selected currency | Optional | Accepts 0 or more. |
| Site works and utilities | selected currency | Optional | Accepts 0 or more. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Area unit and Currency.
- Enter Floor area, Cost per unit area, Contingency and Soft costs.
- Optionally add Land cost and Site works and utilities.
- Select Calculate.
Worked example
A 2,400 sq ft house at $185 per sq ft, 10% contingency, 15% soft costs, $28,000 site works, $120,000 land.
- Area
- 2400
- Rate
- 185
- Contingency
- 10
- Soft
- 15
- Site works
- 28000
- Land
- 120000
Hard cost $444,000, soft $66,600, site $28,000 = $538,600, plus $53,860 contingency = $592,460 build, or $712,460 with land.
Reading the result
- Land is deliberately excluded from "total build cost" so this figure can be compared against build-only quotes even when the land itself was bought at a very different time or price.
- The build-rate table shows how sensitive the total is to the entered rate alone — useful for stress-testing a quote against a higher rate before committing, without having to re-enter every field.
Assumptions and limitations
- Cost per unit area is a single blended rate applied uniformly across the whole floor area — it does not distinguish higher-cost spaces like kitchens and bathrooms from lower-cost ones like garages or storage.
- Soft costs and contingency are both modelled as flat percentages rather than independently estimated line items, so unusually complex permitting or design work is under-represented if the default percentage is left unchanged.
Common mistakes
- Using a national or generic average rate for a bespoke or high-specification build — custom finishes can run several times a standard-spec rate, and this calculator has no way to know which one was entered.
- Mixing area definitions — gross floor area versus livable or conditioned area can differ by 15–20%, and using a rate quoted for one against an area measured in the other silently changes the effective cost per square foot.
Frequently asked questions
What contingency should I use?
10% for a straightforward new build on a clean site, 15–20% for renovations or anything with unknowns behind existing walls.
Why is the all-in cost per square foot so much higher than the build rate?
Because the quoted rate usually covers construction only. Soft costs and contingency typically add 25–30% before land is even considered.