Planning & Budgeting
Build Project Budget Calculator
Estimates total project budget from a base cost, contingency, and GST/HST
Updated June 26, 2026 · Live
What this tool does
Estimates total project budget from a base cost, contingency, and GST/HST.
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How the build project budget calculator works
Estimates a total project budget from a base cost, a contingency percentage, and GST/HST. The calculator applies your figures to a standard budgeting formula — contingency is added to the base cost, then GST/HST is applied to that subtotal — and shows each line separately. Every figure is an estimate, and final scope always moves the number.
Typical Canadian contingency allowances
Budget "wastage" is called contingency. Typical allowances: 10% on a new kitchen or bathroom, 15% on a single-storey addition, 20% or more on heritage-designated or change-of-use work. Our defaults reflect common Canadian allowances, and can be adjusted upwards for older properties or uncertain scope, or downwards where the scope is well defined.
What this tool does not do
It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm National Building Code (NBC) compliance. Those remain the responsibility of a suitably qualified designer, surveyor, or your building inspector.
On-site considerations for a build budget
Fixed-price quotes are rare on renovation work. Most jobs are let on a schedule of rates with a provisional sum for unknowns, so it is worth knowing which model your contractor is using before you fix a budget.
the National Building Code (NBC) and compliance
Domestic projects over $100,000 that involve more than one contractor are notifiable under provincial OH&S regulations. The client (you) has legal duties even on a domestic project. When in doubt, a pre-application enquiry to the municipality can give early clarity, which tends to be less costly than retrospective correction.
Before you commit
Three written quotes on identical specifications help catch pricing differences — verbal quotes are effectively unenforceable if the job then goes wrong. Cross-checking this budget against those quotes highlights where your assumptions on scope, contingency, or GST/HST treatment differ from the contractor's.
Adjusting the defaults
Every input in this calculator is editable. Enter your own base cost, contingency percentage, and GST/HST rate — the output recalculates instantly. If the defaults feel off for your project type, your own numbers always override them.
Using this build project budget calculator alongside other BuildMetricLab tools
This calculator works best as part of a planning workflow. Pair this budget with our material-cost, labour-cost, and project-timeline calculators to build a complete picture before you commit. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.
Sources & methodology
Estimates a total project budget as C = B·(1+c)(1+t): contingency is added to the base cost B, then GST/HST is applied to that subtotal. Every result is calculated from the values you enter, and all inputs are editable.
Frequently asked questions
Are build project budget calculator results accurate enough to set a budget?
Use them as a starting estimate only. Confirm the figure with written quotes from your contractor or suppliers before committing — actual prices, scope changes and site conditions all move the final cost.
What contingency percentage should I use?
Contingency covers unforeseen costs, not material offcuts. Typical Canadian allowances are around 10% on a new kitchen or bathroom, 15% on a single-storey addition, and 20% or more on heritage-designated or change-of-use work. Raise it for older properties or where the scope is still uncertain.
Does this replace professional advice?
No. This tool is a planning estimator. For works that affect structure, the National Building Code (NBC), property-line or shared-wall, gas, electrics, drainage to a sewer, or similar, consult a suitably qualified professional.
Can I change the unit prices?
Yes — every price field is editable. Plug in your supplier's quote to get a total that matches your project.
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