ADU Calculator California
Build a California ADU planning estimate from floor area, construction rate, design and permit allowances, utility work, site work and contingency. Enter your own assumptions to produce a transparent scenario estimate.
Fill in the required fields to see your result.
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The primary output summarizes the selected scenario. Supporting outputs expose intermediate calculations so the result can be checked.
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How to Use This Calculator
Enter current figures using the units shown. Review assumptions, compare scenarios and inspect the supporting outputs before interpreting the result.
Formula & Methodology
The calculator applies the formulas shown in the result logic to your inputs. It does not add hidden market, tax, lending or regulatory assumptions.
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.
Planning estimate only. Actual outcomes may vary because of taxes, fees, rates, plan rules, regulations, market performance, property conditions and professional methods.
Educational planning tool only. Verify current information and obtain qualified professional advice before making financial, tax, legal, lending, investment, construction or real-estate decisions.
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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