Renovation cost calculator

How renovation cost is estimated in Australia

The fastest way to budget a renovation is the cost-per-square-metre method: take the internal floor area you're touching and multiply it by a rate that matches the scope of work. It's the same shorthand builders and quantity surveyors use for a first-pass figure, and it's good enough to decide whether a deal is worth chasing before you pay anyone to quote it properly. The rate is doing all the heavy lifting, though, so the whole exercise lives or dies on picking a realistic one.

For a sanity check on the numbers, the Archicentre Australia CostGuide (2026) puts renovations within an existing home at roughly $1,600–$3,900/m², and extensions or new construction higher again at about $2,700–$5,100/m². The rates below sit inside those bands and are what the calculator uses by default.

The three scopes, and where the rate goes wrong

A cosmetic refresh — paint, new kitchen and bathroom, flooring, light fittings, no walls moved — sits around $2,000/m². A full renovation where you're relocating walls, re-plumbing and rewiring runs closer to $3,500/m². Structural work and extensions — new footings, a second storey, opening up the back of the house — start around $5,000/m² and climb from there with the finish level. The mistake I see most is a flipper pricing the job they want (cosmetic) on a house that actually needs the job it has (full or structural). Walk the property assuming the worse of the two until a builder tells you otherwise.

Two things the flat rate doesn't capture on its own. First, PC and PS items — tapware, appliances, tiles, stone — where the same layout can swing thousands depending on selections; budget these deliberately rather than letting a showroom set them. Second, a small floor area makes wet areas look disproportionately expensive, because a kitchen and bathroom carry most of the cost into a handful of square metres. On a compact flip the $/m² average can understate what those two rooms really take.

The Sydney and Melbourne premium

Metro labour rates in Sydney and Melbourne run roughly 10–25% above the national base, and site access constraints — no parking, narrow streets, nowhere to stage a skip bin — can add another 5–10% before you've bought a single fixture. If you're flipping in an inner-metro suburb, nudge the scope rate up before you trust the total, and get a real quote earlier than you would in a regional market.

Contingency is not optional

Every flipper underestimates, and older housing stock is where it bites. 10% contingency is the floor; on anything built before about 1980 where you're opening up walls, budget 15–20%. That's the buffer for the things you can't see at inspection — rewiring an old fuse board to current standards, re-stumping, asbestos in the eaves or vinyl, rusted-out drainage, a roof that fails once you're up there. You don't have to spend the contingency, but you have to have it, because a reno blowout eats the margin the resale was supposed to deliver.

The cost the reno number leaves out: time

A renovation budget prices the works, not the calendar. Every extra week the project runs, you're still paying interest, rates, insurance and utilities on a house that isn't earning — the deal's holding costs. Scope creep is really schedule creep, and schedule creep is a second, quieter cost line that never shows up in a $/m² estimate. Build the timeline honestly and hold the reno figure and the holding figure side by side.

Where the reno number sits in the deal

The renovation cost is one of the two big variables in a flip — the other is what you pay for the house. Get it wrong and everything downstream is wrong: the 70% rule backs your maximum purchase price out of the after-repair value minus the reno, so an optimistic reno figure quietly tells you to overpay. Feed a realistic number into the flip ROI calculator and you're comparing profit after real costs, not a headline margin. And your resale target — the after-repair value — has to justify the scope you're pricing here, or the spend doesn't pencil. You can see how the reno budget flows through a full feasibility on a real listing in the sample analysis, and the whole process start to finish in the guide to flipping a house in Australia.

This is general information, not construction, financial or tax advice. Renovation rates vary widely by scope, finish, site conditions and location, and change over time. Figures here are indicative ranges current at the time of writing — always get a fixed-price quote from a licensed builder for your specific property before you commit.