Setback Calculator
Enter your plot’s frontage and depth and the setbacks from your local rules. The setback calculator subtracts them to give the buildable envelope, its area and share of the plot, and opens that envelope as a room in the floor plan editor.
Setback calculator
Planning aid, not a compliance check; FAR/FSI, coverage and setbacks are set by your local development rules. Not checked: height-dependent setbacks, corner plots, road widening, projections allowed into setbacks.
Bare numbers are meters; 190 mm works too.
Your figure, if your rules set one. Leave blank to skip.
Assumptions
Change any value to match your product or local rules.
Basis: Example only: setbacks depend on your plot size, road, building height and local rules; replace with yours.
Basis: Example only: setbacks depend on your plot size, road, building height and local rules; replace with yours.
Basis: Example only: setbacks depend on your plot size, road, building height and local rules; replace with yours.
Basis: Example only: setbacks depend on your plot size, road, building height and local rules; replace with yours.
- Buildable width
- 12.00 m
- 39′ 4″
- Buildable depth
- 25.00 m
- 82′
- Buildable area (envelope)
- 300.00 m²
- 3,229.2 sq ft
- Share of the plot
- 66.67%
- What limits the footprint
- Setbacks (no coverage entered)
- Largest footprint
- 300.00 m²
- 3,229.2 sq ft
With the setbacks you entered, the buildable envelope is 12.00 m (39′ 4″) × 25.00 m (82′), 300.00 m² (3,229.2 sq ft) or 66.67% of the plot.
Design this room
- Opens a room whose outer wall faces sit on the setback lines. Draw your rooms inside it. The editor measures walls on their centre lines, so the room is 0.15 m smaller each way than the envelope.
How this was calculated
- Buildable width = plot width − left setback − right setback
- Buildable depth = plot depth − front setback − rear setback
- Buildable area = buildable width × buildable depth; share = ÷ plot area
- With a coverage figure: largest footprint = the smaller of the buildable area and plot area × coverage ÷ 100
- Buildable width = 15.00 m − 1.50 m − 1.50 m = 12.00 m
- Buildable depth = 30.00 m − 3.00 m − 2.00 m = 25.00 m
- Buildable area = 12.00 m × 25.00 m = 300.00 m²
- Share of the plot = 300.00 m² ÷ 450.00 m² × 100 = 66.67%
- Largest footprint = buildable area = 300.00 m²
How it works
Enter the plot
Frontage is the width along the road; depth runs back from the road.
Enter your setbacks
Front (road side), rear, left and right, each from your rules. The defaults are examples only.
Read the envelope
Buildable width = width − left − right. Buildable depth = depth − front − rear. The area is width × depth.
Add coverage if you have it
With a coverage figure, the largest footprint is the smaller of the envelope and plot × coverage, and the calculator names which one limits you.
Worked example
A 15 × 30 m plot (450 m²) with a 3 m front setback, 2 m at the rear and 1.5 m on each side: the envelope is 15 − 1.5 − 1.5 = 12 m wide and 30 − 3 − 2 = 25 m deep. That is 300 m², 66.67% of the plot, about 3,229.2 sq ft. Add a 60% coverage figure and the footprint is capped at 450 × 60 ÷ 100 = 270 m², so coverage is the limit.
In feet: a 40 × 60 ft plot (2,400 sq ft) with 15 ft at the front, 10 ft at the rear and 5 ft on each side leaves 30 × 35 ft, or 1,050 sq ft (43.75%, 97.548192 m²).
What setbacks are
A setback is the strip between a plot boundary and the building that you keep clear. Rules usually set the front setback from the road edge of the plot and the rear and side setbacks from the other boundaries, each measured at right angles to the boundary. The building has to stay inside the rectangle they leave, called the envelope.
Envelope or coverage: which one limits you
Setbacks fix where you can build; coverage fixes how much of the plot you can cover. On a deep plot with small setbacks, the envelope can be larger than the coverage figure gives, and coverage is the limit. On a narrow plot, the side setbacks bite first. Enter both and the calculator names the one that limits your footprint.
Irregular and corner plots
This calculator works on rectangles. For a plot that tapers or has angled sides, enter its narrowest width and shortest depth: the envelope you get then fits inside the real one, so the result errs on the small side. Corner plots often have two road sides with front-style setbacks on both; enter that road side’s setback as the side setback for that side.
Draw inside the envelope
“Design this room” opens the envelope in the floor plan editor as one room. The editor draws walls on their centre lines with 150 mm walls, so the room opens 150 mm smaller each way and its outer wall faces sit on the setback lines. Draw your rooms inside it. Envelopes over 100 m a side are larger than the editor’s rooms, so the button stays off.
Frequently asked questions
How do I calculate buildable area after setbacks?
Take the left and right setbacks off the plot width and the front and rear setbacks off the depth, then multiply. A 15 × 30 m plot with 3, 2, 1.5 and 1.5 m setbacks leaves 12 × 25 m, 300 m².
What is the difference between a setback and ground coverage?
A setback sets how far the building stays from each boundary. Coverage sets what share of the plot the building may cover. You can meet one and still be over the other.
Do balconies or sunshades count inside the setback?
Rules differ. Some let sunshades, balconies or steps project a set distance into a setback, others do not. This calculator does not check projections.
How are setbacks measured?
Usually from the plot boundary to the building, at right angles to the boundary. Your rules say which face of the building to measure to.
What if my plot is not a rectangle?
Enter the narrowest width and the shortest depth. The envelope then fits inside the real one, so the area it gives is on the small side.
Ready to plan your space?
It is free, runs in your browser and needs no account. Projects are saved privately on this device.