Buildable envelope calculator
Enter a lot area, FSR, height limit and setbacks and see the buildable GFA, footprint, storeys, unit count and parking load — plus which constraint binds first. Free, no login, printable.
Buildable envelope calculator
Density bindsDensity binds before height: FSR caps you at 54,450 sf, reachable in 5 of the 6 permitted storeys, so 17,424 sf of height envelope sits unused.
Buildable GFA
54,450 sf
5 storeys on plate
Footprint
11,979 sf
coverage governs
Units
61
@ 750 sf net
Parking
43 stalls
15,050 sf consumed
| Lot area × FSR21,780 × 2.5 | 54,450 sf |
|---|---|
| Footprint after setbacks(132 − 2×3m) × (165 − 5m − 6m) | 14,663 sf |
| Footprint at max coverage21,780 × 55% | 11,979 sf |
| Height-constrained GFA11,979 sf × 6 storeys | 71,874 sf |
| FSR-constrained GFAlot area × FSR | 54,450 sf |
| Buildable GFAlesser of the two | 54,450 sf |
| Net saleable54,450 sf × 85% | 46,283 sf |
| Unit count46,283 ÷ 750 sf | 61 |
| Required stalls61 × 0.7 | 43 |
| Parking area43 × 350 sf | 15,050 sf (28% of GFA) |
Verify before you rely — this is indicative feasibility arithmetic on the numbers above, not a planning opinion. Overlays, heritage designations, site-specific exceptions, bonusing and approvals all move the answer. Confirm every figure with the municipality and a qualified planner before you transact.
Density sensitivity
| FSR | Buildable GFA | Units | Binds |
|---|---|---|---|
| 1.50 | 32,670 sf | 37 | fsr |
| 2.00 | 43,560 sf | 49 | fsr |
| 2.50 | 54,450 sf | 61 | fsr |
| 3.00 | 65,340 sf | 74 | fsr |
| 3.50 | 71,874 sf | 81 | height |
No bylaw figures are pre-filled here: every number above is yours. Zonelor only pre-fills a zone when a reviewed row with a source URL and an observation date exists.
02What the calculator is doing
Feasibility fails in one of two places, and almost never in the place people check first. Density is the number everyone quotes, but on a shallow or narrow lot the setback rectangle collapses the footprint, and the height limit then caps you well below the FSR the bylaw advertises. The calculator computes both paths in parallel and names the one that binds.
Parking is the second silent tax. Stalls are derived from the unit count, not the lot, so a higher FSR can raise your stall requirement faster than it raises saleable area. The parking row shows the gross area those stalls consume as a share of the envelope.
How these figures were produced
- Modelled — Derived arithmetically from observed inputs using the published method; not a market quote.
03Carry the envelope forward
04Questions
Frequently asked
What does 'binding constraint' mean?
Two separate rules cap your building: density (lot area × FSR) and height (buildable footprint × permitted storeys). The smaller number is what you can build. Whichever produces it is the binding constraint, and the gap between the two is GFA the bylaw permits on paper but the site cannot deliver.
How is the footprint calculated?
The lot is treated as a rectangle: depth equals lot area divided by frontage. Side setbacks are deducted from both sides, front and rear setbacks from the depth. That footprint is then capped by the site coverage rule, and the smaller of the two governs.
Where do the numbers come from?
Every input is yours unless you arrive from a zone page, in which case reviewed bylaw figures are pre-filled and cited with a source URL and an observation date. Zonelor never pre-fills a figure that a human has not promoted.
Is the unit count reliable?
It is arithmetic, not an architectural yield study: buildable GFA × efficiency ÷ average unit size, rounded down. Real yield moves with core layout, corridor geometry, unit mix and parking configuration. Treat it as the ceiling, not the plan.
Not advice — Zonelor is a data publisher. Figures are indicative benchmarks for comparison, not professional advice, and must be confirmed with a qualified professional before you rely on them. About Zonelor