A construction budget built line by line, at your rates
A cost per square foot is a starting guess, not a budget. This page builds the project properly: the main works priced on the project area, then the parts a single rate always hides (demolition, electrical points, plumbing fixtures, heating and cooling, the kitchen and bathroom allowances where renovation budgets go to die, flooring, painting, site works, professional fees and permits), each at a rate you enter from quotes or recent local jobs. There are no built-in prices: construction costs are fiercely local, and an invented rate would poison every line beneath it. The estimate applies any minimum charge openly, adds contingency once and tax once, and reports the total, a low to high range and the all-in cost per square foot, with a downloadable estimate for comparing builders.
Main works and demolition
Services: electrical, plumbing, heating and cooling
Kitchen, bathrooms and finishes
Site, professional fees and permits
Minimum, contingency, tax and range
Disclaimer: This calculator gives estimates for general information only. It is not financial, medical or other professional advice. A budget built on your own rates is a planning tool; structural work needs proper drawings and, where your jurisdiction requires it, licensed professionals and permits before work begins.
What this calculator does
It assembles a construction or renovation budget from measured quantities and entered rates, keeping the two separate so each can be argued with on its own evidence. The main works line prices the area at your shell rate; every system and finish that a bare per-square-foot figure smuggles in unexamined is then given its own line with its own unit (points, fixtures, rooms, square feet, flat allowances), because those are the lines where real budgets are won and lost. Professional fees and permits sit visibly in the build-up rather than arriving later as ambushes, contingency applies once to the whole rather than being padded secretly into every line, and the all-in cost per square foot falls out at the end, where it belongs: as a check on the itemized budget, not a substitute for it.
How to use it
- Start from the scope, not the rate. Walk the project room by room and system by system, counting what the lines ask for: the area, the points, the fixtures, the rooms getting allowances. Disagreements with a builder’s quote usually turn out to be scope disagreements wearing price costumes, and counting first is how you find out before signing.
- Allowances are decisions, not leftovers. The kitchen and bathroom lines carry allowances because their cost is chosen, not measured: the same room can absorb a modest allowance or five times it in cabinets, stone and appliances. Enter what you genuinely intend to spend, and treat any builder’s placeholder allowance in a quote as the number most likely to grow during the job.
- Renovation and new build are different animals at the same square footage. Renovation carries demolition, unknowns inside existing fabric, and trades working around a standing structure; its rates and its sensible contingency are both higher. This page does not force a rate on either, but the contingency hint and the range exist because renovation totals that pretend to new-build certainty end as disputes.
- Professional fees are part of the project cost. Design, engineering, surveys and permits commonly run to a noticeable slice of the whole; a budget that omits them is not leaner, it is unfinished. Enter them as flat amounts from actual proposals where you have them.
- Compare builders on the same lines. Convert each quote into these lines (asking the builder to itemize where they will not) and the differences localize: one builder’s area rate, another’s allowances, a third’s missing site works. The downloadable estimate is built for that side-by-side work.
How it is calculated
- Each line = its quantity x its rate, rounded to cents: main works and demolition, flooring and painting per square foot; electrical per point; plumbing per fixture; kitchen and bathrooms per room at their allowances. Heating and cooling, site works, professional fees, permits and other charges enter as flat amounts.
- Subtotal = the sum of the line amounts. Minimum charge: if a minimum is entered and exceeds the subtotal, the minimum becomes the base and the results state that the minimum charge applied.
- Contingency = the contingency percentage applied once to the base. Tax = the tax percentage applied once to base plus contingency, when entered.
- Total = base + contingency + tax. Range = total less and plus your percentage. Cost per square foot = total / the project area, the all-in figure including fees and contingency.
Worked examples
A full project, priced. Illustrative rates, entered as a user would from quotes: main works on 1,500 square feet at $180 ($270,000.00); demolition of 300 square feet at $8 ($2,400.00); 40 electrical points at $150 ($6,000.00); 12 plumbing fixtures at $850 ($10,200.00); heating and cooling $12,500; one kitchen at a $28,000 allowance; two bathrooms at $9,500 each ($19,000.00); flooring 1,200 square feet at $9 ($10,800.00); painting 1,500 at $3.50 ($5,250.00); site works $15,000; professional fees $9,000; permits $2,800. Subtotal $390,950.00. Contingency at 10% adds $39,095.00 for a total of $430,045.00, which is $286.70 per square foot all-in, ranging from $365,538.25 to $494,551.75 at plus or minus 15%.
The square foot that checks the budget. Note what the example’s all-in $286.70 does: it began as a $180 main-works rate and grew by the services, allowances, fees and contingency that per-square-foot rules of thumb silently assume. Comparing your all-in figure against quoted per-square-foot figures for finished projects is fair; comparing your bare main-works rate against them is how budgets are born $100,000 light.
A small renovation meets the floor. A flooring-only refresh, 200 square feet at $9, is $1,800 of lines; against a contractor’s $2,500 minimum the estimate builds on the minimum, adds 10% contingency ($250.00) and totals $2,750.00, stating that the minimum charge applied.
Reading your results
Read the lines as shares of the whole: in most whole-house projects the main works dominate and should; when allowances rival the structure in size, the project is a finishes project wearing a construction costume, and its risk sits in choices, not in building. Then read the all-in per-square-foot figure against completed local projects of similar specification (the only honest benchmark there is), and read the high end of the range as the number your financing should survive. If a builder’s total lands far below your itemized build-up, the missing money is somewhere specific: a line they excluded, an allowance they placeholder-priced, or hours and scope they have not yet met on site.
Limitations
- Ground and structure hold vetoes. Foundations in poor soil, structural surprises in existing fabric, and utility connection charges can each add sums no line here predicts. Drawings, a site visit and, for renovations, opening-up inspections are what convert this budget structure into a price.
- Specification is a dial on every rate. The same square foot exists at wildly different costs depending on finishes, fixtures and tolerances. The page deliberately carries no specification presets, because a preset would smuggle invented prices back in; your quotes set the level.
- Financing, escalation and time are outside the total. Interest during construction, price escalation on a long build, temporary housing during a renovation: real costs of the episode, carried in the other-fixed-charges line only if you put figures to them.
- Nothing here replaces permits or professionals. The estimate budgets the fees; it does not do the design, the engineering or the approvals, and work that needs them needs them regardless of what any calculator says.
Frequently asked questions
How much does it cost per square foot to build or renovate?
There is no portable figure: it swings with region, specification, structure and whether the square feet are new or existing. The honest way to get yours is the one this page performs: price the main works at a quoted local rate, itemize the systems and allowances on top, add fees and contingency, and divide. On this page’s worked example that road leads from a $180 main-works rate to $286.70 per square foot all-in, which is the kind of gap that makes borrowed rules of thumb dangerous.
What is usually included in a builder’s per-square-foot price?
Less than most people assume, and it varies by builder: typically the structure and standard finishes for the area, with some mix of services included and allowances standing in for kitchens, bathrooms and fixtures. The only safe reading of any per-square-foot quote is its own inclusions list. This page’s lines mirror the usual exclusions and allowances so you can rebuild any quote on a consistent basis and see what its headline rate leaves out.
How much contingency should a renovation carry?
More than a new build, because the unknowns are physical and hidden: rot, wiring, plumbing and structure that only reveal themselves when opened. Ten percent is a floor for a straightforward renovation with the fabric already inspected; fifteen to twenty is common planning practice where little has been opened up. On a clean new build with fixed drawings and known ground, a smaller allowance is defensible, and this page applies whatever you set once, openly, rather than burying it in rates.
Are professional fees and permits part of the construction cost?
Yes, in every complete accounting of a project: design and engineering make the work buildable and lawful, and permits and inspections are not optional extras. They are routinely forgotten in early budgets because they arrive before the visible work starts, which is why this page gives them their own lines in the build-up rather than a note at the end.
Related calculators
Method: itemized quantity times rate lines at user-entered rates, minimum charge applied to the base, contingency once and tax once, exactly as defined on this page. Last reviewed: 13 October 2026.