California ADU
Calculators + Sources
Use these bounded planning tools to organize project inputs and compare them with selected state-law conditions. Verify the current local ordinance, agency guidance, site constraints, and application status.
ADU Planning Calculators
Each route states its source basis, inputs, limitations, and review date. A planning result is not a permit determination.
Start with the current state framework and local implementation
California reorganized its ADU statutes into Government Code §§ 66310–66342. HCD guidance explains the statewide framework, while the local agency applies current law and valid local standards to the project.
- Identify whether the proposal is an ADU, JADU, conversion, new detached unit, or another statutory pathway.
- Confirm the parcel, zoning, existing development, transit context, fire access, utilities, coastal status, and other project facts.
- Read the current HCD guidance and cited Government Code section rather than relying on an older section number.
- Verify the local ordinance, application checklist, fees, effective dates, and written agency determination.
ADUs, JADUs, conversions, and new detached units do not share one universal rule set. Select the correct pathway and verify all conditions and exceptions in the current statute and local implementation.
A numeric condition may be only one part of the decision. Existing legal conditions, building and fire codes, utilities, recorded constraints, coastal requirements, and local application evidence can still matter.
Source and review basis
Hub claims reviewed .