Ontario | Zoning districts

Ontario, California Zoning Districts: Residential Zones, Homes per Acre, Minimum Densities, Allowed Uses, Mixed-Use Zones and Overlays

A zoning district, or zone, is the set of rules that says what may be built on a lot. In the City of Ontario, in San Bernardino County, those rules are the Ontario Development Code. The City posts its own copy, one PDF per chapter, on its Development Code page. This page lists the eight residential zones, the range of homes each one requires and allows, the uses each permits, the mixed-use zones, and the overlays that change the rules on some lots. The Ontario overview has the summary.

The Eight Residential Zones

Sources: Ontario Development Code, Section 6.01.010, Table 6.01-1 and Table 6.01-3 (Rev. 08.18.2026). The lot columns are the standards for a traditional single-family lot. Multiple-family projects use a project area in place of a lot size.

Section 5.01.005 establishes the districts and gives each one a purpose. The words below are the code's own.

• AR-2. The district is for "single-family residences on large lots, at a density range of 0 to 2.0 dwelling units per acre" with "limited agricultural activities and animal keeping within a rural environment."
• RE-2. The district is for "single-family residences on larger lots" in "a semi-rural environment where limited animal keeping is permitted."
• RE-4. The district is for "single-family homes on estate-sized lots, in a suburban environment, at a density range of 2.1 to 4.0 dwelling units per acre."
• LDR-5. The district is for "single-family homes on individual lots, in a suburban environment, at a density range of 2.1 to 5.0 dwelling units per acre."
• MDR-11 and MDR-18. Each is for "a variety of attached and detached housing types, in a suburban environment."
• MDR-25. The district is for "higher density residential developments, in a more urbanized environment, at a density range of 18.1 to 25.0 dwelling units per acre."
• HDR-45. The district is for "high-density multiple-family developments in an urban environment, generally located within 1/2-mile of a transit corridor or station."

How the Density Range Works on a Lot

Density is the number of homes for each acre of land, and an acre is 43,560 square feet. Ontario gives every zone a range with a minimum and a maximum. Chapter 9.0 defines residential density as "the minimum and maximum number of allowed dwelling units for each net acre of land." A net acre leaves out street right-of-way and land dedicated to the public. The same definition sets the rounding: for the minimum, "the number shall be rounded up, to the higher whole number," and for the maximum, "the number shall be rounded down, to the lower whole number."

• The minimum is a rule. A note to each standards table reads: "A residentially zoned lot shall be developed at no less than the minimum number of dwelling units allowed within the specified density range for the applicable zoning district." If the shape of the lot makes that impossible, "the lot may be developed with a maximum of one dwelling unit."
• A small lot still gets one home. "Lots with a maximum density calculation of less than one dwelling shall be allowed the construction of one dwelling unit."
• Old lots keep their rights, with a limit. For a traditional house lot, an existing lot below the minimum size "shall be granted all development rights of the zoning district in which it is located." For multiple-family projects the note is narrower: a substandard lot keeps the zone's rights, "except that the maximum density shall be limited to the minimum number of dwelling units allowed within the specified density range."
• Houses in the two highest zones. Section 5.03.365 allows a single-family dwelling in MDR-25 and HDR-45 only on a legally established lot that is below the minimum area or too small to reach the density range.
• ADUs are counted separately. An accessory dwelling unit that meets Section 5.03.010 will not be "Deemed to exceed the allowable density for the lot."

Three examples, as VanPlex arithmetic from the tables. An LDR-5 lot of 7,200 square feet is 0.165 acres, and 0.165 times 5.0 is 0.83, so the lot holds one home. An MDR-18 lot of 10,000 square feet is 0.2296 acres: the minimum is 0.2296 times 11.1, or 2.55, rounded up to three homes, and the maximum is 0.2296 times 18.0, or 4.13, rounded down to four. An MDR-18 lot of 7,500 square feet is below the 10,000 square foot project area, so the note limits it to the minimum: 0.172 times 11.1 is 1.91, rounded up to two homes. Ask the Planning Department to confirm the count for a real lot, because the tables print "per acre" and the definition says "net acre."

What Each Zone Permits

Table 5.02-1, the Land Use Matrix, groups the eight zones into four columns. P means the use "is permitted by right of being in the proper zoning district." C means it needs a Conditional Use Permit, a permit decided after a public hearing. A row of dashes in the matrix means the use "is expressly prohibited." A use the matrix leaves out "shall be deemed a prohibited use" unless the Zoning Administrator allows it.

Source: Ontario Development Code, Section 5.02.010, Table 5.02-1, page 5.02-6 (Rev. 08.18.2026). Mobilehome parks are permitted only in the MHP district.

• What multiple-family means. Chapter 9.0 defines multiple-family dwellings as "Two or more attached dwelling units, with each dwelling designed for occupancy by independent households," and adds that they "shall not include accessory dwelling units." A duplex is therefore a multiple-family use.
• What single-family means. A single-family dwelling is "A single detached dwelling unit," and the definition covers "small lot and cluster developments consisting of two or more detached dwelling units, regardless of the number or configuration of lots."
• Two-unit projects. The matrix has no row for the state SB 9 two-unit project. Section 5.03.403 allows it in a single-family residential zoning district, and the ADUs and SB 9 page has the rules.
• Projects of three or more homes. A P in the matrix still leaves a design review. Section 4.02.025 requires Development Plan approval for "The development of 3 or more dwelling units on a single lot." See the permits and fees page.

Mixed-Use Zones

Sources: Ontario Development Code, Section 5.01.005.C (Rev. 08.19.2025) and Section 6.01.020.C (Rev. 08.18.2026).

A Planned Unit Development, or PUD, is a document the City Council adopts for one site with its own standards. In MU-1, MU-3, MU-6, MU-8B, MU-8C and MU-8E the code says "development shall occur only after a Planned Unit Development has first been adopted for the affected property." MU-1 is divided into four land use areas: Euclid Avenue Entertainment, Arts, Holt Boulevard and Civic Center. The matrix permits multiple-family dwellings in every mixed-use column but the south part of the Arts area, which sits between two rail lines. The City's Planned Unit Developments page posts 15 adopted PUDs.

Two commercial zones also take homes. The matrix lists residential mixed-use developments in CN and CC with a Conditional Use Permit, and Section 5.03.285 sets the number of homes case by case: "the maximum residential density shall be determined based upon an Equivalent Impact Study (EIS) prepared for the project," which compares "traffic generation, water usage, and sewerage generation" with the commercial floor area allowed. The three or more homes page covers these zones.

Overlays and Special Districts

An overlay district is a second set of rules that applies on part of the map in addition to the base zone. Section 5.01.005 lists seven. Four matter for housing.

• AH, Affordable Housing. The overlay covers sites in the City's housing inventory "south of Riverside Drive," "along East Holt Boulevard between the Cucamonga Creek Channel and Corona Avenue," and the MU-8C land at West Holt Boulevard and Mountain Avenue. There, "all new residential development, regardless of affordability, requires a minimum density of 20 dwelling units per acre." Affordable housing projects "shall be allowed by right." Tier 1 means at least 20 percent of the homes are for lower income households for at least 30 years, and Tier 2 means at least 25 percent.
• ICC, Interim Community Commercial. The overlay keeps older commercial buildings in use. New housing there "shall first require a zone change to the HDR-45 zoning district."
• AG, Agriculture. The overlay keeps farming in place until land develops. It permits a "Single dwelling unit on a lot not less than 10 acres in area," and any other new building needs a specific plan first.
• EA, Euclid Avenue, and CNO, Chino Airport. These add historic and airport rules. See the airport zones and specific plans page.

Two specialized districts hand the rules to another document. In the SP (Specific Plan) district, development follows "the standards and guidelines of the applicable Specific Plan document," and the City's Specific Plans page lists 52 plans. In the PUD district, development is allowed only under the adopted PUD. A third district, MHP, is for mobile home communities "at a density range of 5.1 to 11.0 dwelling units per acre," with a minimum project area of 3.0 acres.

The Zoning Map and Changing a Zone

• The map. Section 5.01.010 adopts the "City of Ontario Zoning Map," which "shall be maintained on file in the office of the Planning Department." The Zoning Map page posts a PDF whose file name carries the date July 7, 2026, and an interactive map.
• A 2026 citywide change. The City Council agenda of July 7, 2026 listed the adoption of an ordinance approving File No. PZC25-002, "A CITYWIDE ZONING MAP AMENDMENT TO IMPLEMENT THE ONTARIO PLAN 2050 POLICY PLAN AMENDMENT." The minutes of that meeting were not read for this guide.
• Unclear boundaries. A boundary shown along a street "shall be construed as following the centerline of the right-of-way," and where doubt remains "the Zoning Administrator shall determine in writing, the location of the boundary in question."
• Confirming a zone. The City's Planning FAQs say "Because some properties are governed by a specific plan or other special regulations, contact the Planning Department to confirm the applicable requirements before designing or submitting a project." The fee schedule lists a Zoning/Land Use Verification Letter at $222.60.
• Rezoning. A zone change is a legislative action: the Planning Commission recommends and the City Council decides, under Table 2.02-1. The fee schedule lists $14,554.05 for less than 5 acres and $16,050.30 for 5 acres or more, each with public hearing fees added.

Where the Code Disagrees With Itself

Section 1.01.015 gives the rule for these cases: "Where any conflict occurs within the provisions of this Development Code, the more restrictive provision shall apply." Ask the Planning Department how it reads each one.

• Alley-loaded and cluster houses in LDR-5. Section 6.01.010 says the small lot alley-loaded and cluster standards apply "within the LDR-5, MDR-11, MDR-18, MDR-25, and HDR-45 zoning districts," and Tables 6.01-2B and 6.01-2C print an LDR-5 column. The Land Use Matrix marks both uses prohibited in the RE-4 and LDR-5 column.
• Names of the mixed-use zones. Section 5.01.005 lists MU-1, MU-3, MU-6, MU-8B, MU-8C, MU-8D and MU-8E. The purpose text of Section 6.01.020 still names an "MU-2 zoning district" for East Holt and an "MU-11 zoning district" for Euclid/Francis at "14 to 25 DU/AC" and up to 3 stories, while the standards for MU-8D in the same section print 20.0 to 75.0 homes per acre and up to 5 stories.
• MU-6 minimum density. Section 5.01.005 prints "14 to 40 DU/AC" for MU-6. Section 6.01.020 prints "a minimum allowed density of 14.1 dwelling units per acre."
• Table and section numbers. Section 6.01.010 refers to "Table 5.01-1 (Land Use Matrix)," and the matrix is Table 5.02-1. Section 5.02.005 refers to "Section 5.01.015 (Zoning Map Adoption)," and the map is adopted in Section 5.01.010.
• A chapter that stops early. In the posted Chapter 6.0 file, the Affordable Housing Overlay text ends on page 6.01-86 partway through the Tier 2 rules, and the next page in the file is Division 6.02. The overlay list in Section 5.01.005 has a seventh district, the Chino Airport Overlay, with no standards section in the posted Division 6.01.

Limits of This Page

The Development Code was read from the City's own PDFs. The Chapter 5.0 and 6.0 files are named "Rev 08-18-2026," the pages of Division 5.01 print "Rev. 08.19.2025," and Chapter 9.0 is dated August 19, 2025. City Council agendas from January 7, 2025 to October 6, 2026 were read for later changes, and none of the three agendas after August 18, 2026 lists a Development Code amendment. The Zoning Map itself, The Ontario Plan land use map, the 52 specific plans and the 15 PUD documents were not read, so this page gives no zone for any address. The rest of the Ontario Municipal Code is hosted by an outside publisher whose site blocks scripted requests, and it was not read.

Where to Go Next

Related on VanPlex: the Ontario overview, the California lot eligibility page and the California SB 9 page.

Frequently Asked Questions

Official sources (checked October 2026)