Bihar Building Byelaws Calculator

Q: How many floors can I build on a 20 ft road in Patna?

On a 20 ft (6.1 m) road the byelaw table allows FAR 2.0, up to G+3 or stilt + 3 and 12 m height; small plots may get fewer floors after setbacks.

Q: Is the Bihar Building Byelaws 2026 in force?

No. It was published as a draft and has not been notified; the 2014 byelaws with amendments apply.

Enter your plot and road width. See how much you can build, how tall, how many floors, and the setbacks you must leave, as per the Bihar Building Byelaws 2014 and their amendments.

Rules updated October 2026Patna & all Bihar townsFree, no sign-up

Plot

Plot width * The side of the plot that faces the road. Side setbacks are fixed by this width. Plot depth * From the road to the back boundary. Front and rear setbacks are fixed by this depth.

Width of the road in front * Measure the full road between the boundary walls on both sides, not just the paved part. This one number decides FAR, height and whether commercial use is allowed. If two roads touch the plot, enter the wider one. Area type * The byelaws have separate tables for Old Area and New Area, as notified by your planning authority. Old areas allow construction from a 12 ft (3.6 m) road; new areas need at least 20 ft (6.1 m). Not sure? Old areas are the long-built parts of town; colonies developed on fresh land are usually new areas. Location Used only to point you to the right authority. The byelaws are the same across Bihar.

Building

Use * Commercial and other non-residential uses need a road of at least 40 ft (12.2 m) in Bihar (cl. 33(5)). Floors you plan * Floors above ground, not counting a stilt parking floor. Height is estimated at 3.0 m per floor (3.6 m for commercial) plus a 0.45 m plinth.

Stilt parking on the ground floor (adds a level to the height; excluded from FAR when used only for parking) Basement (checks the minimum plot size and boundary gap)

How this calculator works

Each result comes from a specific table in the Bihar Building Byelaws 2014, as amended, including Notification 10713 of October 2025, which added premium FAR on wider roads. Measurements are converted to metres, because the byelaws are written in metres.

Road width picks the row in Table 15 (Old Area) or Table 16 (New Area). That row gives the FAR, maximum height and whether commercial use is allowed.
Height is the lower of the table limit and, on roads of 9.1 m or more, 1.5 × (road width + front setback) (cl. 39).
Setbacks come from Table 8 (front and rear, by plot depth) and Table 9 (sides, by plot width), in the column for your building's height. Above 15 m, the high-rise open-space table (Table 14) applies all round.
Buildable area per floor is what is left after the setbacks. Bihar's byelaws do not set a separate ground-coverage percentage; coverage follows from the setbacks.
Maximum floors is the smaller of (plot area × FAR ÷ buildable area per floor) and the floors that fit within the height limit.

FAR and height by road width (Bihar)

Road width	Residential FAR	Commercial FAR	Floors / height
12 ft (3.6 m), old area	1.5	Not allowed	G+2 / 10 m
16 ft (4.8 m), old area	1.8	Not allowed	G+2 / 10 m
20 ft (6.1 m)	2.0	Not allowed	G+3 or S+3 / 12 m
30 ft (9.1 m)	2.5	Not allowed	S+5 / 18 m
40 ft (12.2 m)	2.5 (up to 3.0 with premium)	2.0 (up to 2.5)	24 m
60 ft (18.3 m)	2.5 (up to 3.5)	2.5 (up to 3.0)	No fixed cap
80 ft (24.4 m), new area	3.0 (up to 4.0)	2.5 (up to 3.5)	No fixed cap

Old areas: no new construction on roads under 12 ft. New areas: no new construction on roads under 20 ft (cl. 33). Premium FAR is bought at 10% (residential) or 15% (other uses) of the MVR rate for the extra area.

Residential setbacks for a typical Patna plot

Plot depth	Up to 10 m tall (G+2): front / rear	Up to 12 m (G+3)	Up to 15 m (G+4)
Up to 10 m (33 ft)	1.5 / 0.9 m	Not permitted	Not permitted
10–15 m (33–49 ft)	1.5 / 1.2 m	2.5 / 1.8 m	Not permitted
15–21 m (49–69 ft)	1.8 / 1.5 m	3.6 / 2.0 m	4.0 / 3.0 m
21–27 m (69–89 ft)	2.5 / 1.8 m	4.0 / 2.5 m	4.5 / 3.6 m

Side setbacks depend on plot width. Plots up to 10 m (33 ft) wide need none for buildings up to 10 m tall. Plots 10–15 m wide need 0.75 m on each side up to 10 m height and 1.5 m up to 12 m.

Other rules the calculator checks

Rainwater harvesting is mandatory on every plot (cl. 51).
High-rise means 15 m or more. It needs a plot of at least 800 m², open space all round, a fire NOC and lifts.
Basement on an individual residential plot needs at least 500 m² of plot and must keep 3 m from the boundary (cl. 47).
Stilt parking and basements used for parking are not counted in FAR (cl. 38(10)).
Balconies are not allowed where the setback is under 1.5 m. They may be 0.6 m deep for setbacks of 1.5–2.5 m and 0.9 m above 2.5 m.

Questions people ask

What is FAR in Bihar?

FAR (Floor Area Ratio) is total built-up area on all floors ÷ plot area. With FAR 2.0 on a 1,200 sq.ft plot, you can build 2,400 sq.ft in total across all floors.

How many floors can I build on a 20 ft road in Patna?

On a 20 ft (6.1 m) road, the byelaw table allows FAR 2.0, up to G+3 (or stilt + 3) and 12 m height. A small plot may get fewer floors once setbacks are taken out. Enter your plot above to see the exact number.

Can I open a shop on a narrow road?

Under the 2014 byelaws, commercial and other non-residential uses need a road of at least 12.2 m (40 ft). A May 2026 amendment for commercial buildings has been reported; confirm with your authority before planning.

Is the Bihar Building Byelaws 2026 in force?

No. It was published as a draft for objections and has not been notified. Until it is, the 2014 byelaws with their amendments apply. We will update this calculator when it is notified.

Does stilt parking count in FAR?

No. Stilt and basement areas used for parking are excluded from FAR. The stilt still counts in the building's height.

Sources

Bihar Building Byelaws 2014, Urban Development & Housing Department (Patna Metropolitan Area Authority copy): pmaa.bihar.gov.in
Notification 10713 dated 04-10-2025 (premium FAR, Tables 17A–17C): Patna Metropolitan Area Authority downloads
Patna BPAS portal (byelaws, fee calculator, airport zones): automap.bihar.gov.in