San Francisco — Density & Dwelling Units

Last reviewed: July 6, 2026

Overview

This page explains how the San Francisco Planning Code regulates the number of homes you can build on a lot (dwelling-unit density) and related standards like group housing, unit mix, and density exceptions. It focuses on what the Planning Code itself establishes; for zoning maps and broader background, see the San Francisco Planning Code and Use Districts.

In most San Francisco districts, the Planning Code ties maximum units to lot area (for example, one unit per 800, 600, 400, or 200 sq ft), with special rules for group housing and a citywide exception that lets most RH lots build up to four homes (six on corners) without a state density bonus under § 207(c)(8).

How San Francisco measures residential density

• Lot-area-per-dwelling-unit control. The Code sets a maximum number of units by requiring a minimum lot area for each unit. Common control levels in Article 2 tables include one unit per 800, 600, 400, or 200 sq ft of lot area (district-specific; see breakdown below). The same tables often specify that if a district doesn’t list its own R controls, the project may use the density “permitted in the nearest R District.”
• Group housing density. Where “group housing” is permitted, the Code uses bedrooms-per-lot-area, not dwellings. Typical control levels are one bedroom per 275, 210, 140, or 70 sq ft (district-specific). Examples are documented for RM-3 (1 per 140) and RM-4 (1 per 70).
• Accessory Dwelling Units (ADUs). ADU eligibility and quantity are governed by §§ 207.1 and 207.2; most use tables list ADUs as permitted per those sections. See the separate San Francisco ADUs page for how ADUs stack with base density.
• Dwelling unit mix. For projects at certain sizes, the Planning Code requires a distribution of 2- and 3-bedroom units. The tables repeatedly reference § 207.7 as the controlling standard.

Other requirements that interact with density—like height/bulk, exposure and open space, yards/setbacks, and upper-story sculpting—are covered separately under Height & Bulk and Setbacks & Yards. Building-safety limits are in the California Building Standards Code.

District-by-district: Dwelling-unit density and related standards

RH (Residential, House) districts — RH-1, RH-1(D), RH-1(S), RH-2, RH-3

• Purpose and character: Not found in retrieved materials.
• Typical permitted uses: Dwelling uses are permitted per the residential use tables citing § 102; see district tables for story-by-story listings.
• Base density controls (lot area per unit or per lot):
  • The RH family uses explicit caps by units-per-lot and minimum lot area (per Article 2 tables referencing §§ 102, 207). Summarized controls include:
    • RH-1 / RH-1(D) / RH-1(S): up to one unit per lot; or one per 3,000 sq ft; limited total units are noted in the table.
    • RH-2: up to two units per lot; or one per 1,500 sq ft.
    • RH-3: up to three units per lot; or one per 1,000 sq ft.
• Key density exception in RH districts:
  • Residential Density Exception — up to four units per lot (six on corner lots) when a project is not using a state or local density bonus, plus a specified group-housing bedroom ratio in RH‑1 variants. See § 207(c)(8)(A) for eligibility and conditions; historic-resource and tenant protections apply, and new units are placed under a regulatory agreement tied to the Rent Ordinance.
• Group housing density (where allowed): Example ratios are shown in Code interpretations and tables; for RH-3 the group-housing control is one bedroom per 275 sq ft of lot area; the RH density exception also lists 1 bedroom per 415 sq ft for RH‑1 family districts when using the exception. Verify applicability for your RH subtype.
• Where it applies: Mapped citywide where the Zoning Map shows RH-1, RH-1(D), RH-1(S), RH-2, or RH-3. Verify with the Planning Department and the Use Districts.

RM (Residential, Mixed) districts — RM-1, RM-2, RM-3, RM-4 (Article 2, § 209.2)

• Purpose and character: RM districts “recognize, protect, conserve and enhance” mixed house/apartment areas; RM-1 is low density, RM-2 moderate, RM-3 medium, RM-4 high density, as detailed in § 209.2.
• Typical permitted uses: Residential uses; supporting nonresidential uses in keeping with each district’s character. See § 209.2 descriptions.
• Base density controls (lot area per unit, per Article 2 tables referencing §§ 102, 207):
  • RM-1: one unit per 800 sq ft of lot area (explicit in a district-specific affordable housing SUD that measures its bonus against RM‑1’s 1:800 baseline).
  • RM-2: district is described as “moderate density”; multiple Article 2 tables show a 1:600 control in districts of similar intensity; confirm for a specific parcel. Not found in retrieved materials as a standalone RM-2 statement.
  • RM-3: one unit per 400 sq ft of lot area (confirmed in Code interpretation for RM‑3).
  • RM-4: one unit per 200 sq ft of lot area (confirmed in Code interpretation for RM‑4).
• Group housing density (Article 2 tables referencing § 208):
  • RM-1 level districts commonly show one bedroom per 275 sq ft; RM-2 level districts show one per 210; RM-3 is one per 140; RM-4 is one per 70. Examples are confirmed for RM‑3 (1:140) and RM‑4 (1:70).
• Where it applies: Mapped citywide in areas labeled RM-1 through RM-4; check the Zoning Map and the Use Districts.

RC (Residential-Commercial) districts — RC-3, RC-4 (Article 2, § 209.3)

• Purpose and character: RC districts combine residential with neighborhood-serving commercial uses; RC-3 mirrors RM-3 intensity; RC-4 mirrors RM-4. § 209.3 also notes no off-street parking requirements as part of the mixed-use character.
• Typical permitted uses: Residential uses with supporting commercial; see § 209.3 and district tables.
• Base density controls (by cross-reference to RM controls in § 209.3):
  • RC-3: follows RM-3 character; use 1 unit per 400 sq ft where the table so provides.
  • RC-4: follows RM-4 character; use 1 unit per 200 sq ft where the table so provides.
• Group housing density: Mirrors the RM level (e.g., 1:140 for RC‑3, 1:70 for RC‑4) where permitted.
• Where it applies: Mapped in specific mixed-use neighborhoods; confirm on the Zoning Map and see Use Districts.

Special situations that change or supplement base density

• Senior housing. Many district tables allow “up to twice” the number of dwelling units otherwise permitted when the housing is specifically designed for and occupied by seniors, citing § 202.2(f) alongside § 207.
• “Nearest R District” fallback. Several mixed or commercial tables cap residential density at “the density permitted in the nearest R District,” with a minimum of one unit per 800 sq ft where applicable. This is explicitly reflected in Article 2 tables for multiple non‑R districts.
• Special Use Districts (SUDs). Certain SUDs modify or remove density caps. Example: in the Van Ness SUD there is “no density limit” noted in the district table; always check Special Use Districts.
• Division or loss of units. Article 2 tables cross-reference § 317 for demolition/merger and § 207.8 for certain divisions of existing units. Check Conditional Use triggers and neighborhood-specific limits.

Key numbers at a glance (selected districts)

Practical notes

• Many mixed and commercial districts list density like “1 per 800/600/400 sq ft, or the density of the nearest R District, whichever is greater,” and pair it with group-housing bedroom ratios (e.g., 1 per 275/210/140). Check the applicable use table for your mapped district.
• Separate standards—usable open space per unit, exposure, yards, height/bulk—will further shape how many units “fit.” See Height & Bulk, Setbacks & Yards, and Design Standards.

Checklist

• Identify the mapped district(s) (e.g., RH-2, RM-3, RC-4) on the Zoning Map; confirm any Special Use Districts.
• Pull the Article 2 use table row for “Dwelling Units” in your district; note the lot-area-per-unit ratio and any “nearest R District” fallback.
• If pursuing RH projects, assess eligibility for the four-/six‑unit RH density exception under § 207(c)(8); confirm historic resource, unit-replacement, and Rent Ordinance regulatory-agreement requirements.
• If proposing group housing, apply the bedroom-per-lot-area ratio for your district level. Confirm allowed use.
• Confirm ADU eligibility and limits under §§ 207.1–207.2; factor in unit mix if § 207.7 applies.
• Cross-check height/bulk, exposure, open space, yards, and any Conditional Use triggers that can constrain practical unit count.
• Verify building and fire-life-safety constraints with San Francisco Construction Requirements and the California Building Standards Code.

Risks & Ambiguities

Plain-English Summary

San Francisco counts homes by lot area: the district’s ratio (like one unit per 800, 600, 400, or 200 sq ft) sets a hard cap, unless a local exception or SUD says otherwise. In single‑family RH areas, a city exception now lets most lots build up to four homes (six on corners) if you meet the extra rules. ADUs are handled under separate ADU sections, and big projects may have to include a mix of 2‑ and 3‑bedroom units. Height, yards, and open‑space rules still limit what actually fits on a site.

Source References

• San Francisco Planning Code — Article 2 use tables and district purposes: §§ 102, 207, 207.1, 207.2, 207.7, 208, 209.1, 209.2, 209.3 (see Planning Code; density rows and district purposes cited above).
• RH districts — RH density exception: § 207(c)(8).
• RM district baselines — RM‑1 (1:800) referenced in SUD; RM‑3 (1:400) and RM‑4 (1:200) confirmed in interpretations; group-housing ratios confirmed for RM‑3 and RM‑4.
• RC districts — mirror RM controls per § 209.3.
• Van Ness SUD reference (no density limit note in table).

Retrieved passages

• San Francisco Zoning Code (§ 102) High relevance show source text
• San Francisco Zoning Code (§ 102) High relevance show source text
• San Francisco Zoning Code (§ 102) High relevance show source text
• San Francisco Zoning Code (§ 102) High relevance show source text
• San Francisco Zoning Code (§ 207) High relevance show source text
• San Francisco Zoning Code (§ 102) High relevance show source text
• San Francisco Zoning Code (§ 151.1) High relevance show source text
• San Francisco Zoning Code (§ 102) High relevance show source text
• San Francisco Zoning Code (§ References) High relevance show source text
• San Francisco Zoning Code (§ 102) High relevance show source text
• San Francisco Zoning Code (§ 151) High relevance show source text
• San Francisco Zoning Code (§ 138.1) High relevance show source text
• San Francisco Zoning Code (§ 135) High relevance show source text
• San Francisco Zoning Code (§ 102) High relevance show source text
• San Francisco Zoning Code (§ 207) High relevance show source text
• San Francisco Zoning Code (§ References) High relevance show source text
• San Francisco Zoning Code (§ 303) High relevance show source text
• San Francisco Zoning Code (§ References) High relevance show source text

Cited sections

• San Francisco Planning Code — Article 2 use tables and district purposes: §§ 102, 207, 207.1, 207.2, 207.7, 208, 209.1, 209.2, 209.3 (see Planning Code; density rows and district purposes cited above). (Article 2)
• RH districts — RH density exception: § 207(c)(8). (§ 207)
• RM district baselines — RM‑1 (1:800) referenced in SUD; RM‑3 (1:400) and RM‑4 (1:200) confirmed in interpretations; group-housing ratios confirmed for RM‑3 and RM‑4.
• RC districts — mirror RM controls per § 209.3. (§ 209.3.)
• Van Ness SUD reference (no density limit note in table).
• SF Planning Code.md