What does the ADU Calculator California calculate?

Build a California ADU planning estimate from floor area, construction rate, design and permit allowances, utility work, site work and contingency.

Is this result guaranteed?

No. It is a planning estimate based entirely on the assumptions you enter. Actual costs, returns, taxes, rates, regulations and outcomes can differ.

Can I change the assumptions?

Yes. Replace every default or example value with current figures specific to your situation and compare multiple scenarios.

Should I make a financial decision from this result alone?

No. Verify the figures and consult qualified financial, tax, legal, lending, construction or real-estate professionals where appropriate.

How to Use the ADU Calculator California

Learn how to use the ADU Calculator California, check its formula and interpret the result.

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How to use this calculator

Open the ADU Calculator California, enter current figures and review every assumption before using the result. Supporting outputs show how the estimate was produced.

Formula

The calculator uses transparent arithmetic based on the values entered. It does not silently insert a lender quote, tax rule, contractor price, market forecast or legal conclusion.

Worked example

This is an editable budget model, not a statement of current California fees or legal eligibility. Enter quotes and allowances specific to the property and jurisdiction.

Before acting on the result

Check dates, units, rates and costs. Compare multiple scenarios and obtain current professional advice where the decision is material.

Limitations

This calculator is educational and for planning. It is not financial, investment, tax, legal, lending, appraisal, construction or real-estate advice.

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Frequently Asked Questions

What does the ADU Calculator California calculate?: Build a California ADU planning estimate from floor area, construction rate, design and permit allowances, utility work, site work and contingency.
Is this result guaranteed?: No. It is a planning estimate based entirely on the assumptions you enter. Actual costs, returns, taxes, rates, regulations and outcomes can differ.
Can I change the assumptions?: Yes. Replace every default or example value with current figures specific to your situation and compare multiple scenarios.
Should I make a financial decision from this result alone?: No. Verify the figures and consult qualified financial, tax, legal, lending, construction or real-estate professionals where appropriate.

Last updated 7/21/2026