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What can you build on a Chicago lot?

Enter a lot size and a zoning district. You get the setbacks, floor area, height, unit count, open space, parking and uses that district allows — every figure cited to the section of the ordinance it comes from.

The calculator

Lot size and district

Two inputs decide most of what the zoning code allows on a vacant lot: how big the lot is, and which district it sits in. Everything below is the ordinance applied to those two facts — the same engine that runs on a real parcel inside LotGrade, with the parcel-specific parts left out and named.

Look a district up in the Zoning Field Guide, or find your parcel’s on the city’s zoning map.

Lot size

Give the width and depth, or the total area — whichever you know. Filling in one clears the other.

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Choose a zoning district above — the lot is already set to the standard 25 × 125 ft Chicago lot, so change it only if yours differs. The setbacks, floor area, height, units, open space, parking and permitted uses appear here.

Or jump straight to a worked example: RT-4, 25 × 125 ft.

Where each figure comes from

How the answers are derived

Nothing here is a rule of thumb. Each line is one standard in Title 17, applied to the lot size you gave.

OutputHow it is derivedSection
SetbacksThe district’s own yard rules, applied to your dimensions: a share of lot depth in front and rear, a share of lot width at the sides, each with its floor and its cap.§17-2-0305
Minimum lot areaThe floor on lot size in R districts. B, C, D and M districts set none.§17-2-0301
HeightThe district figure, measured to the ceiling joist of the top floor on a flat roof. In B and C districts the limit moves with the lot’s frontage.§17-17-0311
Floor areaLot area × the district’s floor area ratio — the total floor area of the principal buildings, not the footprint.§17-17-0257
Dwelling unitsLot area ÷ the district’s minimum lot area per unit, rounded down. Efficiency and SRO units carry lower figures in RT-4 and up.§17-17-0304
Rear yard open spaceRS, RT, RM-4.5 and RM-5 only: the greater of a per-unit figure or a percentage of the lot, holding a circle of a given diameter.§17-2-0307
ParkingThe residential ratio for the district’s parking group, times the unit count, before any of the reductions below.§17-10-0207
UsesThe permitted (P) and special (S) columns of the district’s use table, summarized to its headline uses.§17-3-0207

Each output, the rule behind it, and the section to read.

Parking

Ways to reduce the parking requirement

The parking figure above is the by-right requirement with no relief claimed. Chicago writes several reductions directly into the ordinance — most of them do not need a hearing, and the transit one routinely takes a residential project to zero.

  • Transit-served location§17-10-0102-B

    Within 2,640 ft of a CTA or Metra rail entrance, or 1,320 ft of a listed CTA bus corridor: the minimum ratio may be reduced by up to 100% outside downtown (50% for Metra, and 50% in D districts, beyond which it is an administrative adjustment). Bicycle parking is required in exchange.

  • Affordable units§17-10-0102-B

    Where half the units are affordable, assisted, or income-restricted at or below 80% of area median income, the ratio may be reduced by up to 100% on a transit-served site.

  • Landmark buildings§17-10-0102-A

    No additional parking for the rehabilitation or reuse of a Chicago Landmark or a contributing building in a landmark district; up to 50% off for National Register rehabilitations.

  • Accessible (Type A) units§17-10-0102-F

    A building using the Type A unit incentives is capped at one space per 8 ft of alley frontage, with an accessible space counting as two.

  • In D districts, all-underground parking cuts the ratio by half, and buildings of 100+ small units can be cut by a further 25%. Below 5, 10 or 50 spaces (by dash number) the requirement is waived outright.

  • Administrative adjustment§17-13-1003-CC

    The Zoning Administrator can drop a house’s two-space requirement to one where it buys usable open space, and can shave spaces in other listed cases — a counter application, not a hearing.

Fractions round to the nearest whole space, with 0.5 rounding up (§17-10-0402). Reductions are applied to the ratio before the count, so they compound with the unit count rather than after it.

The limits

What a district and a lot size cannot tell you

A calculator knows the rulebook. It does not know the block. These are the things that regularly move the answer on a real parcel, in rough order of how often they bite:

  • The block’s own front yards

    In RS districts the required front yard is the average of the nearest lots on the block, with no fixed alternative; in RT, RM and DR that average is an option beside the fixed figure. It needs the neighbors’ buildings, not the rulebook.

  • Which line is the front

    A corner, through or reversed corner lot re-points the front, the rear and the street side yard. A reversed corner lot owes a street-side yard set from the lot behind it.

  • Overlays and bonuses

    Transit-served density and floor area under Connected Communities, the 606 and Pilsen demolition-surcharge rules, landmark districts, and neighborhood-specific overlays all sit on top of the base district.

  • Planned developments

    Inside a PD the negotiated ordinance governs, not the underlying district, and above a threshold height or unit count a PD is mandatory.

  • The lot’s own history

    Lot of record status, an existing legal nonconforming building, an alley, an easement, a shared PIN or an assemblage of several parcels all change what is actually buildable.

  • The building already there

    Demolition, an existing footprint worth keeping, and what the floor area of that building already uses up are all facts about the parcel, not the district.

For a real address

Run it on a real parcel

Give LotGrade a Chicago address and it does this with the parcel’s own facts: the real lot shape and area from the county, the front yard averaged from the neighboring buildings, the corner and reversed-corner rules applied to the right line, the overlays and bonuses the site qualifies for, the existing building, ownership and sales history, and the buildable envelope drawn in 3D — with a pro forma on top of it. Contiguous lots can be assembled and run as the single site they would become.

Analyze a Chicago address Book a walkthrough

The analyzer requires an account — you’ll be asked to sign in. The Zoning Field Guide, the zoning code and these guides are free and need no login.

Questions

Common questions

How do I find my lot’s zoning district?

Chicago publishes its zoning map, and every parcel carries a district like RS-3 or B2-3. The Zoning Field Guide lists all 70 districts with their figures, and LotGrade reads the district straight off the parcel when you look up an address.

Is the front setback really the district number?

Often not. In RS districts §17-2-0305 makes the front yard the average of the nearest two lots on either side, leaving out the shallowest, and that average governs however deep it is. In RT, RM and DR districts the owner chooses between that average and the fixed 15 ft or 12% of lot depth. A calculator that only knows the district and the lot size cannot see those neighbors; the district figure is the starting point, not the answer.

How many units can I build on my lot?

Divide the lot area by the district’s minimum lot area per dwelling unit and round down — 3,125 sq ft in RT-4, at 1,000 sq ft per unit, is three units. Efficiency and SRO units carry lower figures in RT-4 and above, and a coach house or conversion unit can add one more where the district allows it (§17-17-0304).

Does this include TOD or Connected Communities?

No. This page applies the base district to the size you enter. Transit-served density and floor area bonuses, the 606 and Pilsen rules, landmark districts and planned developments all depend on where the parcel sits, so they need the parcel itself.

Can the setbacks or the parking be reduced?

Yes, by named routes: administrative adjustments for small deviations decided at the counter, variations heard by the Zoning Board of Appeals, special uses, and the parking reductions in §17-10-0102. See variations, special uses and planned developments.

Is a zoning calculator enough to underwrite a deal?

It is enough to screen one. Before you buy, the numbers that move a pro forma are the contextual front yard, the overlays, the existing building and the lot’s recorded history — which is what a parcel-level analysis adds.

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