California ADU Lot Coverage Calculator
Check ADU and JADU footprint against California lot coverage, setback and floor area limits, including SB 9 lot-split allowances.
- ADU Max
- 1,200 sqft
- Detached, by right
- JADU Max
- 500 sqft
- Within main home
- Rear Setback
- 4 ft
- ADU minimum
Formula & Statutory Rule
Formula
coverage_pct = (main + adu) / lot_area × 100
Statutory Rule
adu_max = 1,200 sqft; jadu_max = 500 sqft; rear_setback = 4 ftRegional Benchmark Reference
| Jurisdiction / Tier | Rate or Limit | Statutory Note |
|---|---|---|
| Detached ADU | 1,200 sqft | By right |
| JADU | 500 sqft | Within home |
| Rear setback | 4 ft | Minimum |
Frequently Asked Questions
How large can an ADU be?
A detached ADU may be up to 1,200 square feet by right, subject to local height and setback rules.
What is a JADU?
A junior ADU is a unit up to 500 square feet created within the existing footprint of a single-family home.
Do ADUs count toward lot coverage?
Many jurisdictions exempt ADUs up to a threshold from lot coverage calculations; check the local ordinance.
What is SB 9?
Senate Bill 9 allows a lot to be split and up to two units built per lot in single-family zones, subject to conditions.