🛠️ Free Australian Tools

Free Granny Flat Tools & Calculators

Plan smarter before you talk to a builder. Every tool on this page is free, uses real Australian state rules, and takes under two minutes to use. No sign-up required.

✅ 11 Free Tools ✅ No Sign-Up Required ✅ NSW · WA · VIC · QLD ✅ AUD & Metric
🔴 Most Popular

Cost, Approval & Size Tools

The three questions every owner asks first — answered instantly.

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Granny Flat Cost Estimator

Select your state, build type, size and fixture level to get an estimated AUD cost range with a full category breakdown.

NSW · WA · VIC · QLD
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Granny Flat Approval Checker

Find out what approval your granny flat needs — CDC, DA, planning permit or none. Covers NSW, WA, VIC and QLD.

NSW · WA · VIC · QLD
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Size & Setback Calculator

Enter your state and lot size to instantly see the maximum allowed granny flat size and minimum setback distances that apply.

NSW · WA · VIC · QLD
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🟠 Investor & Rental Tools

Yield, Finance & ROI Calculators

Run the numbers before you commit — rental yield, loan repayments, and full ROI.

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Rental Yield Calculator

Enter your build cost and expected weekly rent to calculate your annual yield, net weekly income, and estimated payback period.

All States
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Loan Repayment Estimator

See your estimated monthly repayments and total interest for any granny flat loan — adjust the term and interest rate to compare scenarios.

All States
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ROI Calculator

Combine build cost, rental income, and property value uplift to get a full return-on-investment picture over 5, 10, 15 or 20 years.

All States
Coming Soon
🟡 Design Tools

Space Planning & Style Tools

Figure out what fits — and what it should look like.

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Room Space Planner

Select your total granny flat size and layout type to get a suggested room-by-room size breakdown — with links to matching design gallery pages.

All States · Studio / 1 Bed / 2 Bed
Coming Soon
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Style Quiz

Answer 5 quick questions about colour, lifestyle and budget — and find out your granny flat interior style. Scandinavian, Coastal, Japandi and more.

All States
Coming Soon
🟢 Planning & Utility Tools

Timeline, Checklist & Council Lookup

Set realistic expectations and tick every box before you build.

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Build Timeline Estimator

Select your state, approval type and build type to get an estimated week-by-week timeline from design through to occupancy certificate.

NSW · WA · VIC · QLD
Coming Soon
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Planning Checklist

A step-by-step interactive checklist covering every stage of your granny flat project — zoning, quotes, approvals, finance and more. State-specific version included.

NSW · WA · VIC · QLD
Coming Soon
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Council Rules Quick-Lookup

Select your state and council to instantly see the key rules — maximum granny flat size, minimum lot size, setbacks, and approval type — for major Australian councils.

Major Councils — NSW · WA · VIC · QLD
Coming Soon

Ready to Take the Next Step?

Use the tools above to plan your build — then get free quotes from local granny flat builders in your state.

Get Free Builder Quotes →

Frequently Asked Questions

Common questions about our free granny flat tools — answered.

Yes — every tool on this page is completely free. No account, no sign-up, and no credit card required. All tools run directly in your browser using Australian state data built in.
All tools cover New South Wales (NSW), Western Australia (WA), Victoria (VIC) and Queensland (QLD). Each state has its own rules built into the tool — you simply select your state and the correct data applies automatically.
The Cost Estimator uses current Australian per-sqm build rates by state and build type, adjusted for your chosen fixture level. Results are indicative ranges only — actual costs vary significantly by builder, site conditions and material prices. Always get at least three professional builder quotes before committing. See our national cost guide for a full breakdown.
It depends on your state. In NSW, most granny flats go through a CDC (Complying Development Certificate) or DA (Development Application). In WA, planning approval is no longer required for compliant granny flats up to 70sqm — only a Building Permit is needed. In VIC, granny flats up to 60sqm no longer require a planning permit under 2023 reforms. In QLD, secondary dwellings that meet the criteria are Accepted Development — no planning approval required. Use the Approval Checker tool to find out what applies to your specific property.
Maximum sizes vary by state. NSW caps CDC granny flats at 60sqm. WA allows ancillary dwellings up to 70sqm without planning approval. VIC covers small second homes up to 60sqm under the permit-free pathway. QLD (Brisbane) allows secondary dwellings up to 80sqm as Accepted Development on standard lots. Use the Size & Setback Calculator to check the exact rules for your state and lot.
Yes — in all four major states, granny flats can be legally rented to anyone, including people unrelated to the main dwelling occupants. QLD removed occupancy restrictions in 2022. WA, NSW and VIC all permit rental of compliant granny flats. Rental income, yield and payback period can be calculated using the Rental Yield Calculator. Read our full guide on renting out a granny flat in Australia.
No. All tools provide indicative guidance only based on publicly available Australian planning rules and typical build costs as of 2026. Results are not legal, financial or planning advice. Always confirm your specific situation with a licensed builder, private certifier, town planner or your local council before proceeding.