ADU design

500 sq ft ADU plans: what fits, and why 500 matters

By the HyreADU research desk. Last checked October 27, 2026.

The short answer

500 sq ft ADU plans usually hold a 1-bedroom with a full kitchen and bath, or a generous studio.

In California, 500 square feet matters for two rules: a junior ADU can be no larger, and an ADU under 500 square feet of interior livable space is treated as not adding 500 square feet for school fees (Gov. Code § 66311.5(c)(3)). Fresno, Anaheim and Fremont each list a 499 sq ft 1-bedroom.

Agency	Plan near 500 sq ft	Note from the agency page
City of Fresno	Plan 2, 1-bedroom, 499 sq ft	Free
City of Anaheim	Plan 002, 1-bed/1-bath, 499 sq ft	Free
City of Fremont	1-bed/1-bath, 499 sq ft	The one plan listed as usable after the code change
City of Los Angeles	YOU-ADU, 455 sq ft	City-owned and free
County of Sacramento	Laurel and Willow, 460 sq ft	Unincorporated county

What fits in 500 square feet

A bedroom with a closet and an emergency escape window.
A living area that also holds a small dining table.
A one-wall or L-shaped kitchen.
A full bathroom with a shower.
A stacked washer and dryer.

Why so many plans are 499

The 500 square foot mark appears in California law more than once. A junior ADU may be no more than 500 square feet, and under 500 square feet the school fee treatment changes. The larger impact-fee line is 750 square feet. Check your own numbers with the ADU fee calculator.

Interior livable space is the measure

The fee rules count interior livable space, not the outside footprint or porches. Ask your city how it measures, and ask your designer for the interior figure on the plan.

A mistake to avoid

The mistake to avoid is a plan at 501 square feet. Wall thickness, a closet or a mechanical space can push a design over the line. Ask the designer to state interior livable area on the cover sheet and to check it against the city’s definition.

What to do next: check your lot with the ADU feasibility checker, read the questions to ask an ADU builder, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.

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Questions

Is 500 sq ft big enough for a 1-bedroom?

Yes; several agency plans fit one bedroom in 455 to 499 sq ft.

Is a 500 sq ft ADU exempt from fees?

In California, ADUs of 750 sq ft or less pay no impact fees. School fees are a separate rule. Connection charges may still apply.

Can a 500 sq ft ADU have two bedrooms?

It is very tight; agency 2-bedroom plans start near 746 sq ft.

Is a 500 sq ft unit a JADU?

Only if it is inside a single-family house and meets JADU rules.

Sources

City of Fresno, ADU and Small Homes Program. Checked September 5, 2026.
City of Anaheim, Pre-Approved Plan Catalogue. Checked September 5, 2026.
City of Fremont, Preapproved ADUs. Checked September 5, 2026.
LADBS, ADU Standard Plan Program. Checked September 5, 2026.
County of Sacramento, Shelf Ready ADU Program. Checked September 5, 2026.
Gov. Code § 66311.5 (ADU impact fees, connection fees and capacity charges). Checked September 5, 2026.
Gov. Code § 66313 (ADU and junior ADU definitions). Checked October 7, 2026.
HyreADU research: pre-approved ADU plans in California. Checked September 5, 2026.

HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax, lending or engineering advice.

Rules vary by state and city; California rules are labeled as such. Spotted an error? Tell us through our corrections page. Licensed professionals can also contribute as named sources.