Free tool
Chicago FAR calculator
Enter a lot size and a district. You get the maximum floor area the district's floor area ratio permits, the unit count its density standard allows, and its height limit — each read from the Municipal Code with the section cited. Then read the caveats, because on most Chicago lots something other than FAR is what actually stops you.
These are ceilings, not a buildable envelope. Setbacks and the rear-yard open space requirement decide how much of the lot you can occupy; height decides how many floors you can stack; parking binds after that. On a small lot the footprint is almost always what limits you, not FAR. A transit-served location can raise these under Connected Communities, and a parcel inside a planned development is governed by that ordinance instead of its base district.
Districts on this page were read from different sources and on different dates — each district page states its own. Confirm against the current adopted code before relying on a figure. Data snapshot generated 2026-08-24. How this data is produced and checked →
How each number is worked out
| Figure | Calculation | Governed by |
|---|---|---|
| Maximum floor area | lot area × FAR | §17-2-0304-A (R), §17-3-0403-A (B/C), §17-4-0403 (D), §17-5-0403 (M). What counts as floor area: §17-17-0305 |
| Units on density | lot area ÷ min lot area per unit | §17-2-0303-A (R), §17-3-0402-A (B/C). Rounded down; the ordinance does not round up a partial unit |
| Height limit | read from the district table | §17-2-0311-A (R), §17-3-0408-A (B/C). Measurement rules: §17-17-0311 |
The B and C height figure is the most permissive row in §17-3-0408-A — a lot with 100 ft or more of frontage and ground-floor commercial space complying with §17-3-0305. Shorter frontages and buildings without qualifying ground-floor commercial are lower, sometimes by 15 feet. Per-district detail →
What this can't tell you
A calculator knows the district. It does not know the parcel. It cannot see the lot's actual dimensions and how setbacks eat them, a recorded easement, a prior variation, a planned-development ordinance that supersedes the base zoning, or whether the site is a transit-served location. Those are the things that decide a deal.
Run a real address instead → — same ordinance, applied to the parcel's real geometry, with the setbacks and TOD status resolved.
Common questions
- How do you calculate floor area ratio in Chicago?
- Maximum floor area = lot area × the district’s floor area ratio. An RS-3 lot of 5,000 sq ft at an FAR of 0.9 permits 4,500 sq ft of floor area. The arithmetic is the easy part; what counts as floor area is governed by §17-17-0305, and several other standards usually cap a building before FAR does.
- Does the maximum floor area mean I can build that much?
- Rarely. FAR sets a ceiling on total floor area, but setbacks and the rear-yard open space requirement decide how much of the lot you can occupy, and the height limit decides how many floors you can stack. On small lots the buildable footprint, not FAR, is almost always the binding constraint. Parking requirements bind next.
- How many units can I fit?
- The density standard is minimum lot area per unit: lot area ÷ the district’s figure, rounded down. A 5,000 sq ft RM-5 lot at 400 sq ft per unit allows 12 units on density alone — but the same lot’s FAR, height and parking will usually allow fewer. Take the lowest of the constraints, never the friendliest.
- Can the limits be higher than this?
- Yes, in two common cases. A transit-served location under the Connected Communities ordinance can carry FAR, height and density bonuses with reduced parking. And a parcel inside a planned development is governed by that ordinance rather than its base district, which can permit substantially more — or less.
- Why do some districts show no height figure?
- Because the ordinance sets no maximum. §17-4-0407 states plainly that there are no maximum building height limits in the downtown D districts, and §17-2-0311-A sets none for RM-6 and RM-6.5 — in all eleven, tall buildings are governed by planned-development review rather than by a number in a table. Showing an invented ceiling there would understate what those sites can hold, so we show none. The manufacturing M districts likewise carry no residential density standard, because household living is not a general use in them.