How do I calculate total renovation cost per square metre? (Bathroom | Cost & Budget)

If you’ve ever tried to estimate the cost of a bathroom renovation in Sydney based on “per square metre pricing,” you’ve probably discovered something hilarious — and slightly frustrating. Bathrooms are tiny, but somehow the cost per square metre can rival the price of a waterfront penthouse in Darling Point. Welcome to the uniquely spicy world of bathroom renovation maths.

But don’t panic. Calculating cost per square metre isn’t witchcraft. It’s just a mix of logic, construction reality, and a few Sydney-specific quirks. Once you understand how it works, you’ll be able to work out your project budget confidently — without needing a calculator that looks like it came out of NASA.

Let’s break it down like you’re talking to a friendly tradie at Bunnings on a Saturday morning.

1. Why Bathrooms Cost More Per Square Metre Than Any Other Room

First, let’s address the elephant in the room:
A bathroom is usually the smallest room, yet the most expensive per square metre.

Why?
Because it’s the Beyoncé of rooms — high maintenance, full of accessories, and always needing special treatment.

Every square metre includes:

• Waterproofing

• Plumbing

• Electrical work

• Tiling

• Fixtures

• Labour from multiple licensed trades

• High-material density in a small footprint

This means a 4m² bathroom can cost more than renovating 20m² of living room space.

So when people ask, “What’s the cost per square metre?” the honest answer is:
“It depends how fancy your Beyoncé is.”

2. The Formula for Calculating Bathroom Cost Per Square Metre

If you want a clean, simple way to calculate it, use this formula:

Total Renovation Cost ÷ Total Square Metres = Cost per m²

Example:
If your bathroom costs $22,000 and is 4m²:

22,000 ÷ 4 = $5,500 per m²

Sounds simple, right?
But here’s the twist: you can’t calculate this until after you know the overall cost. And the overall cost depends on dozens of variables.

This is why homeowners often ask for per-square-metre pricing first — but contractors can’t give an accurate number without understanding your bathroom’s specifics.

3. Sydney Suburb Differences Affect the Cost per m²

Renovation cost per square metre varies significantly by suburb because of labour rates, access, age of property, and competitive demand.

Sydney examples:

• Eastern Suburbs – labour premium, older buildings, strata complexity

• Northern Beaches – moisture-resistant materials often required

• Inner West – heritage terraces, tricky walls, tight hallways

• North Shore – higher-end finishes, bigger bathrooms

• Western Sydney – lower labour overheads, more standard builds

This means the same 4m² bathroom might range from $3,500/m² to $6,500/m², depending on postcode.

4. Factors that Change Your Bathroom Cost per m²

Think of this as a menu. The more items you pick, the higher the per-square-metre cost climbs.

A. Level of Finish

• Basic: $18k–$25k total

• Mid-range: $25k–$35k

• Premium/luxury: $35k–$60k+

Your tiles, tapware, lighting and layout all influence this.

B. Plumbing Complexity

Staying with existing plumbing saves thousands.
Moving the toilet? The cost per m² jumps faster than housing prices in Marrickville.

C. Waterproofing and Tiling

These two trades make up a big chunk of your bathroom’s cost per square metre.
Large-format tiles? Cheaper to install.
Small mosaic tiles? Beautiful, but your tiler might cry a little — and charge more.

D. Structural Issues

Older Sydney homes (Inner West, Eastern Suburbs, North Shore) often reveal surprises:

• Rotten joists

• Out-of-square walls

• Asbestos

• Poor drainage

• Hidden water damage

These can shift your per-square-metre cost dramatically.

E. Access Conditions

Third-floor walk-up? Narrow staircases?
Trades will both lose calories and increase the labour line item.

5. The Realistic Average Cost per m² in Sydney

A genuine Sydney figure — not the watered-down, too-good-to-be-true number you sometimes see online — generally falls into these ranges:

Bathroom Type Cost per m² (Sydney Average) Budget / Basic $3,000 – $4,500 per m² Mid-range $4,500 – $6,000 per m² High-end $6,000 – $10,000+ per m²

If someone quotes you a full bathroom renovation for under $2,500/m², ask yourself:
“Are they using proper waterproofing? Are they licensed? Or are we about to star in a renovation disaster episode?”

6. Why Cost per m² Isn’t the Best Way to Estimate a Bathroom

Here’s the truth Sydney homeowners eventually realise:
Cost per square metre is a result, not a starting point.

Because bathrooms have so many fixed costs — demolition, waterproofing, toilet installation, electrical upgrades — these don’t change much whether your bathroom is 3m² or 5m².

This means:

• A small bathroom can end up with a higher cost per m²

• A larger bathroom may have a lower cost per m²

Example:
A $22k renovation:

• 3m² bathroom = $7,333 per m²

• 5m² bathroom = $4,400 per m²

Same finish level. Same suburb. Same contractor.
Different cost per square metre.

7. How to Estimate Your Own Bathroom Project

Instead of starting with m², start with these steps:

Step 1: Measure the space

Length × width = total m²
If you have funky angles (common in Sydney terraces), sketch it roughly and estimate.

Step 2: Decide your finish level

Basic, mid-range or luxury?
Be honest — if you love Italian tapware and terrazzo tiles, don’t pretend you can stick to a “basic” budget.

Step 3: Check suburb-specific factors

Older suburbs = potential hidden issues
Strata buildings = extra approvals
Modern homes = more straightforward

Step 4: Plan the layout

Keeping plumbing in the same place?
Congratulations — you just saved $2,000 to $8,000 and lowered your cost per m².

Step 5: Get quotes from licensed contractors

Only then will you see the real per-square-metre cost for your bathroom, not a generic online number.

8. How Trades Calculate Their Cost per m² (Industry Insight)

Here’s the inside secret:
Most trades don’t actually calculate by m².
They calculate by:

• Labour hours

• Material requirements

• Skill level

• Structural difficulty

• Access

• Compliance requirements

Cost per square metre is something homeowners like to understand, so professionals calculate it after quoting.

It’s like trying to price a wedding per guest — it can work, but only after you’ve chosen the venue, the food, the flowers, the photographer and whether Aunt Susan is allowed to sing karaoke.

9. Common Mistakes Sydney Homeowners Make

Avoid these to protect your budget:

Mistake 1: Using online “average m² costs” without local context
Sydney is not Melbourne. Sydney is not Brisbane. Prices here have their own personality — and it's a big, confident personality.

Mistake 2: Thinking smaller bathroom = cheaper renovation
Nope. Small bathrooms can be more expensive per m².

Mistake 3: Ignoring plumbing locations
Reconfiguring a bathroom can turn your budget upside down.

Mistake 4: Forgetting waterproofing rules
Sydney bathrooms must comply with AS 3740. Quality waterproofing increases cost per m² but protects your home for decades.

10. Final Thoughts: Use Cost per m² as a Guide — Not a Rulebook

Calculating cost per square metre for a Sydney bathroom renovation is useful for comparison, but it should never replace a detailed quote. Think of it as checking the weather forecast — helpful, but not always 100% accurate for your exact backyard.

The best way to estimate your bathroom renovation cost per m² is to:

• Understand your space

• Know your finish level

• Consider your suburb

• Maintain your plumbing layout

• Request clear, itemised quotes

• Work with licensed professionals

Do that, and your renovation will be far smoother — and far less likely to blow the budget.

For more information about kitchen, bathroom and house renovation services in Sydney, visit www.mb9.com.au.