Occupant load calculations: BCIN Calculation Lab

Last updated October 22, 2026

When this shows up on the exam

Occupant load is the number of people a floor area is designed for. You rarely get asked for it on its own. More often it is step one of a longer question.

Small Buildings (SB): find the load from the Part 3 table, then use it to size an exit stair, decide if one exit is enough, or decide which way a door swings.
On-site Sewage Systems (OSS): find the number of persons or seats, then multiply by a litres value from Part 8 to get the total daily design sanitary sewage flow.
House: the Part 9 egress articles on stairs, exits and doors use the same load.

The method

Pick the rule that applies. Under OBC Div. B 3.1.17.1.(1) there are three routes:
- assembly space with fixed seats: count the seats;
- a dwelling unit: 2 persons per sleeping room (bedroom);
- everything else: the number the area is designed for, but not less than the value from Table 3.1.17.1, unless it can be shown fewer people will use it. Part 9 repeats the same idea in OBC Div. B 9.9.1.3.
Measure the area. Count mezzanines, tiers and balconies as part of the floor area (3.1.17.1.(3)).
Find the row. Table 3.1.17.1 is grouped by type of use (assembly, care, residential, business, mercantile, industrial, other). Read across to the single column, "Area per Person", in m². Pick the row that matches the use, not the occupancy group name alone. Mercantile has three rows that depend on the storey.
Divide. Occupant load = area in m² divided by m² per person. The code does not state a rounding rule; this guide rounds any fraction up to the next whole person, since a person cannot be split and rounding down would under-count.
Several uses at different times? Work out each one and keep the one that gives the greatest number of persons (3.1.17.1.(4)).
Several areas? Work out each area with its own row, then add.
Use the result. Carry the number into the article that asked for it: stair width (9.8.2.1.(3)), single exit (9.9.8.2.(2)), door swing (9.9.6.5.(1.1)) or sewage flow (Table 8.2.1.3.-A, Table 8.2.1.3.-B).

Worked example 1: a shop on the first storey

A retail store fills the first storey of a building. The sales floor is 296 m². No design load is given.

Rule: neither fixed seats nor a dwelling unit, so use the table (3.1.17.1.(1)(c)).
Lookup: Table 3.1.17.1, Mercantile uses, row "basements and first storeys", value 3.70 m² per person.
Arithmetic: 296 / 3.70 = 80.

Answer: 80 persons. If the same store were on a second storey without a principal entrance from a pedestrian thoroughfare or parking area, or on any higher storey, the "other storeys" row (5.60) would apply instead and the load would drop.

Worked example 2: a hall with a balcony and two uses

A hall has a 240 m² main floor and a 60 m² balcony. It is used for meetings on loose chairs, and sometimes for a banquet with tables.

Step	Working	Result
Area, balcony included	240 + 60	300 m²
Meetings: non-fixed seats, 0.75 m² per person	300 / 0.75	400 persons
Banquet: non-fixed seats and tables, 0.95 m² per person	300 / 0.95 = 315.8	316 persons
Keep the greater	400 vs 316	400 persons

Answer: 400 persons (OBC Div. B 3.1.17.1.(3) and (4)). Leaving out the balcony gives 320, a common trap.

Worked example 3: exit stair width in a Part 9 building

A two-storey Part 9 office building has 558 m² of offices on the second storey. How wide must the required exit stair from that storey be?

Lookup: Table 3.1.17.1, Business and personal services uses, row "offices", 9.30 m² per person.
Load: 558 / 9.30 = 60 persons.
Width by load: 9.8.2.1.(3) uses 8 mm per person: 60 x 8 = 480 mm.
The same Sentence sets a 900 mm floor. Take the greater: 900 mm.

Answer: 900 mm. The per-person width only governs once the load passes 112 persons (900 / 8 = 112.5).

Worked example 4: septic flow for apartments

A building has four apartments, each with 2 bedrooms, on a private septic system.

Load: 2 persons per sleeping room (3.1.17.1.(1)(b)): 4 x 2 x 2 = 16 persons. Note (1) to Table 8.2.1.3.-A sends you to Subsection 3.1.17 for this count.
Lookup: Table 8.2.1.3.-A, row for apartments and other multi-family dwellings, 275 litres per person.
Flow: 16 x 275 = 4,400 L.

Answer: 4,400 L per day. Use the per-person apartment row, not the separate "Dwellings" rows that go by bedroom count.

Common mistakes

Wrong row. Offices (9.30) and personal service shops (4.60) are both Group D but have different rows. Warehouse storage (28.00) is not the same row as general storage (46.00).
Wrong mercantile storey. Basements and first storeys use 3.70. A second storey with a principal entrance from a pedestrian thoroughfare or parking area also uses 3.70. Other storeys use 5.60.
Leaving out the mezzanine or balcony. They count as floor area.
Using the usual use instead of the busiest one when a room changes use, or averaging the uses.
Dwelling units by area or by unit. It is 2 persons per sleeping room, not 2 per unit or 1 per bedroom.
Forgetting the minimum. Stair width is the greater of 900 mm and 8 mm per person.
Treating the 60-person limit as the only test for a single exit. The room area and travel distance limits in 9.9.7.4. also apply.
OSS: picking the lower flow when a row offers two methods. Note (3) of Table 8.2.1.3.-B says use the highest.

Find it fast in the code PDF

Bookmark Division B > Part 3 > Section 3.1 > Subsection 3.1.17. Ctrl+F: occupant load of a floor area, Area per Person, 2 persons per sleeping room, greatest number of persons.
Bookmark Division B > Part 9 > Section 9.8 > 9.8.2.1. Ctrl+F: 8 mm per person.
Bookmark Division B > Part 9 > Section 9.9. Ctrl+F: occupant load of not more than 60 persons, Number and Spacing of Egress Doors.
Bookmark Division B > Part 8 > Section 8.2 > 8.2.1.3. Ctrl+F: calculated using Subsection 3.1.17.

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Code cited in this method

Based on the official 2024 Building Code Compendium on ontario.ca.

OBC Div. B 3.1.17.1. Occupant Load Determination
(1)The occupant load of a floor area or part of a floor area, shall be based on
(a)the number of seats in an assembly occupancy having fixed seats,
(b)2 persons per sleeping room in a dwelling unit, or
(c)the number of persons for which the area is designed, but not less than that determined from Table 3.1.17.1. for occupancies other than those described in Clauses (a) and (b), unless it can be shown that the area will be occupied by fewer persons.
(2)If a floor area or part thereof it has been designed for an occupant load other than that determined from Table 3.1.17.1., a permanent sign indicating that occupant load shall be posted in a conspicuous location.
(3)For the purposes of this Article, mezzanines, tiers and balconies shall be regarded as part of the floor area.
(4)If a room or group of rooms is intended for different occupancies at different times, the value to be used from Table 3.1.17.1. shall be the value that gives the greatest number of persons for the occupancies concerned.
Open OBC Div. B 3.1.17.1. in the code viewer
OBC Div. B 9.9.1.3. Occupant Load
(1)The occupant load of a floor area or part of a floor area shall be based on
(a)two persons per sleeping room or sleeping area in a dwelling unit or suite, and
(b)for occupancies other than as described in Clause (a), the number of persons
(i)for which the area is designed, or
(ii)determined from Table 3.1.17.1.
Open OBC Div. B 9.9.1.3. in the code viewer
OBC Div. B 9.8.2.1. Stair Width
(1)Except as provided in Sentence (2) and Article 9.8.4.7., required exit stairs and public stairs serving buildings of residential occupancy shall have a width of not less than 900 mm.
(2)Exit stairs serving a single dwelling unit or a house with a secondary suite including their common spaces shall have a width of not less than 860 mm.
(3)Except as provided in Article 9.8.4.7., required exit stairs and public stairs serving buildings of other than residential occupancy shall have a width of not less than the greater of
(a)900 mm, or
(b)8 mm per person based on the occupant load limits specified in Table 3.1.17.1.
(4)Except as provided in Article 9.8.4.7., at least one stair between each floor level within a dwelling unit, and exterior stairs serving a single dwelling unit except required exit stairs, shall have a width of not less than 860 mm.
Open OBC Div. B 9.8.2.1. in the code viewer
OBC Div. B 9.9.8.2. Number of Required Exits
(1)Except as provided in Sentences (2) and (3) and Subsection 9.9.9., at least 2 exits shall be provided from every floor area, spaced so that the travel distance to the nearest exit is not more than
(a)40 m in the case of business and personal services occupancies,
(b)45 m for all occupancies where the floor area is sprinklered, and
(c)30 m for all other occupancies.
(2)Except as provided in Subsection 9.9.9., a single exit is permitted from each storey in buildings of 1 and 2 storeys in building height provided the floor area and travel distance requirements conform to those required in Article 9.9.7.4. and the total occupant load served by an exit facility does not exceed 60 persons.
(3)In boarding, lodging or rooming houses,
(a)where sleeping accommodation is provided for not more than eight persons, a single exit is permitted from each floor area, or
(b)where sleeping accommodation is not provided in the basement, a single exit is permitted from the basement floor area.
Open OBC Div. B 9.9.8.2. in the code viewer
OBC Div. B 9.9.6.5. Direction of Door Swing
(1)Except as permitted by Sentence (1.1) and except for doors serving single dwelling unit or a house with a secondary suite, exit doors that are required to swing shall swing in the direction of exit travel.
(1.1)An exit door need not swing in the direction of exit travel where it serves
(a)a room, suite or floor area having an occupant load of not more than 60 persons, or
(b)as part of a means of egress from more than one floor area and the floor areas so served have a total occupant load of not more than 60 persons.
(2)Doors that open onto a corridor or other facility that provides access to exit from a room or suite having an occupant load of more than 60 persons shall swing on the vertical axis in the direction of exit travel.
(3)Doors that divide a corridor that is not wholly contained within a suite shall swing in the direction of exit travel.
(4)Where a pair of doors is installed in a corridor that provides access to exit in both directions, the doors shall
(a)swing in opposite directions, with the door on the right hand-side swinging in the direction of exit travel, or
(b)swing in both directions.
Open OBC Div. B 9.9.6.5. in the code viewer
OBC Div. B Table 8.2.1.3-A. Residential Occupancy — Forming Part of Sentence 8.2.1.3.(1)
Table 8.2.1.3.-A Residential Occupancy — Forming Part of Sentence 8.2.1.3.(1) Residential Occupancy | Volume, litres Apartments, Condominiums, Other Multi-family Dwellings - per person[1] | 275 Boarding Houses (a) Per person, (i) with meals and laundry facilities, or, | 200 Boarding Houses (a) Per person, (ii) without meal or laundry facilities, and | 150 Boarding Houses (b) Per non-resident staff per 8 hour shift | 40 Boarding School - per person | 300 Dwellings (a) 1 bedroom dwelling | 750 Dwellings (b) 2 bedroom dwelling | 1,100 Dwellings (c) 3 bedroom dwelling | 1,600 Dwellings (d) 4 bedroom dwelling | 2,000 Dwellings (e) 5 bedroom dwelling | 2,500 Dwellings (f) Additional flow for[2] (i) each bedroom over 5, | 500 Dwellings (f) Additional flow for[2] (f) (ii) (A) each 10 m² (or part of it) over 200 m² up to 400 m²[3], | 100 Dwellings (f) Additional flow for[2] (f) (ii) (B) each 10 m² (or part of it) over 400 m² up to 600 m²[3], and | 75 Dwellings (f) Additional flow for[2] (f) (ii) (C) each 10 m² (or part of it) over 600 m²[3], or | 50 Dwellings (f) Additional flow for[2] (iii) each fixture unit over 20 fixture units | 50 Hotels and Motels (excluding bars and restaurants) (a) Regular, per room | 250 Hotels and Motels (excluding bars and restaurants) (b) Resort hotel, cottage, per person | 500 Hotels and Motels (excluding bars and restaurants) (c) Self service laundry, add per machine | 2,500 Work Camp/Construction Camp, semi-permanent per worker | 250 Notes to Table 8.2.1.3.-A: (1) The occupant load shall be calculated using Subsection 3.1.17. (2) Where multiple calculations of sanitary sewage volume is permitted, the calculation resulting in the highest flow shall be used in determining the design daily sanitary sewage flow. (3) Total finished area, excluding the area of the finished basement.
Open OBC Div. B Table 8.2.1.3-A. in the code viewer
OBC Div. B Table 8.2.1.3-B. Airports, Bus Terminals, Train Stations, Dock/Port Facilities (Food Services excluded)
Airports, Bus Terminals, Train Stations, Dock/Port Facilities (Food Services excluded) Establishments[1] | Volume, litres (a) Per passenger, and | 20 (b) Per employee per 8 hour shift | 40 Assembly Hall — per seat Establishments[1] | Volume, litres (a) No food service, or | 8 (b) Food service provided | 36 Barber Shop/Beauty Salon Establishments[1] | Volume, litres per service chair | 650 Bowling Alleys (Food Service not included) Establishments[1] | Volume, litres per lane | 400 Churches and Similar Places of Worship — per seat Establishments[1] | Volume, litres (a) No kitchen facilities, or | 8 (b) Kitchen facilities provided | 36 Country Club (excluding Food Service) Establishments[1] | Volume, litres (a) Per resident, | 375 (b) Per employee per 8 hour shift, and | 50 (c) Per member or patron | 40 Day Care Facility Establishments[1] | Volume, litres per person (staff and children) | 75 Dentist Office Establishments[1] | Volume, litres (a) Per wet service chair, and | 275 (b) Per dry service chair | 190 Doctors Office Establishments[1] | Volume, litres (a) Per practitioner, and | 275 (b) Per employee per 8 hour shift | 75 Factory (excluding process or cleaning waters) — per employee per 8 hour shift Establishments[1] | Volume, litres (a) No showers, or | 75 (b) Including showers | 125 Flea Markets[2] (open not more than 3 days per week) Establishments[1] | Volume, litres (a) Per non-food service vendor space, | 60 (b) Per food service establishment / 9.25 m² of floor space, and | 190 (c) Per limited food service outlet | 95 Food Service Operations Establishments[1] | Volume, litres (a) Restaurant (not 24 hour), per seat | 125 (b) Restaurant (24 hour), per seat | 200 (c) Restaurant on controlled-access highway, per seat | 400 (d) Paper service restaurant, per seat | 60 (e) Donut shop, per seat | 400 (f) Bar and cocktail lounge, per seat | 125 (g) Drive-in restaurant per parking space | 60 (i) Cafeteria — per meal | 12 Take-out restaurant (no seating area) Establishments[1] | Volume, litres (h) (i) per 9.25 m² of floor area, and | 190 (h) (ii) per employee per 8 hour shift | 75 Food outlet Establishments[1] | Volume, litres (j) (i) excluding delicatessen, bakery and meat department, per 9.25 m² of floor space, | 40 (j) (ii) per 9.25 m² of delicatessen floor space, | 190 (j) (iii) per 9.25 m² of bakery floor space, | 190 (j) (iv) per 9.25 m² of meat department floor space, and | 380 (j) (v) per water closet | 950 Hospitals — per bed Establishments[1] | Volume, litres (a) Including laundry facilities, or | 750 (b) Excluding laundry facilities | 550 Long-Term Care Homes, etc. Establishments[1] | Volume, litres per bed | 450 Office Building[3] Establishments[1] | Volume, litres (a) Per employee per 8 hour shift, or | 75 (b) Per each 9.3 m² of floor space | 75 Public Parks Establishments[1] | Volume, litres (a) With toilets only per person, or | 20 (b) With bathhouse, showers, and toilets per person | 50 Recreational Vehicle or Campground Park Establishments[1] | Volume, litres (a) Per site without water or sewer hook-up, or | 275 (b) Per site with water and sewer hook-up | 425 Schools — per student Establishments[1] | Volume, litres (a) Day school, | 30 (b) With showers, | 30 (c) With cafeteria, and | 30 (d) Per non-teaching employee per 8 hour shift | 50 Service Stations (no vehicle washing)[3] Establishments[1] | Volume, litres (a) Per water closet, and | 950 (a) Per water closet, and (i) per fuel outlet[4], or | 560 (a) Per water closet, and (ii) per vehicle served | 20 Shopping Centre (excluding food and laundry) Establishments[1] | Volume, litres per 1.0 m² of floor space | 5 Stadiums, Race Tracks, Ball Parks Establishments[1] | Volume, litres per seat | 20 Stores[3] Establishments[1] | Volume, litres (a) Per 1.0 m² of floor area, or | 5 (b) Per water closet | 1,230 Swimming and Bathing Facilities (Public) Establishments[1] | Volume, litres per person | 40 Theatres Establishments[1] | Volume, litres (a) Indoor, auditoriums per seat, | 20 (b) Outdoor, drive-ins per space, or | 40 (c) Movie theatres per seat | 15 Veterinary Clinics Establishments[1] | Volume, litres (a) Per practitioner, | 275 (b) Per employee per 8 hour shift, and | 75 (c) Per stall, kennel or cage if floor drain connected | 75 Warehouse Establishments[1] | Volume, litres (a) Per water closet, and | 950 (b) Per loading bay | 150 Notes to Table 8.2.1.3.-B: (1) The occupant load shall be calculated using Subsection 3.1.17. (2) Flea markets open more than 3 days per week shall be assessed using the volumes stated under the heading "Stores". (3) Where multiple calculations of sanitary sewage volume is permitted, the calculation resulting in the highest flow shall be used in determining the design daily sanitary sewage flow. (4) The number of fuel outlets is considered the maximum number of fuel nozzles that could be in use at the same time
Open OBC Div. B Table 8.2.1.3-B. in the code viewer
OBC Div. B Table 3.1.17.1. Occupant Load
Table 3.1.17.1. Occupant Load Forming Part of Article 3.1.17.1. Type of Use of Floor Area or Part Thereof | Area per Person, m[2] Assembly uses | N/A space with fixed seats | [1] space with non-fixed seats | 0.75 stages for theatrical performances | 0.75 space with non-fixed seats and tables | 0.95 standing space | 0.40 stadia and grandstands | 0.60 bowling alleys, pool and billiard rooms | 9.30 classrooms | 1.85 school shops and vocational rooms | 9.30 reading or writing rooms or lounges | 1.85 dining, beverage and cafeteria space | 1.20 laboratories in schools | 4.60 Care, care and treatment or detention uses | N/A B-1 : detention quarters | 11.60 B-2 : treatment and sleeping areas | 10.00 B-3 : sleeping room areas | 10.00 (See also Article 3.7.1.3.) | (See also Article 3.7.1.3.) Residential uses | N/A dwelling units | [2] dormitories | 4.60 Business and personal services uses | N/A personal service shops | 4.60 offices | 9.30 Mercantile uses | N/A basements and first storeys | 3.70 second storeys having a principal entrance from a pedestrian thoroughfare or a parking area | 3.70 other storeys | 5.60 Industrial uses | N/A manufacturing or process rooms | 4.60 storage garages | 46.00 storage spaces (warehouse) | 28.00 aircraft hangars | 46.00 Other uses | N/A cleaning and repair goods | 4.60 kitchens | 9.30 storage | 46.00 public corridors intended for occupancies in addition to pedestrian travel | 3.70[3] Notes to Table 3.1.17.1.: (1) See Clause 3.1.17.1.(1)(a). (2) See Clause 3.1.17.1.(1)(b) (3) See Note A-3.3.
Open OBC Div. B Table 3.1.17.1. in the code viewer

Show all 9 articles

OBC Div. B 9.9.7.4. Number and Spacing of Egress Doors
(1)Except for dwelling units, at least two egress doors shall be provided where
(a)the area of a room or suite exceeds 200 m² in a Group D, E, F2 and F3 occupancy, or 150 m² in a Group C occupancy, or
(b)the distance measured from any point within a room or suite to the nearest egress door exceeds 25 m.
(2)Doors required in Sentence (1) shall be spaced so that in the event one door is made inaccessible by a fire within such a room or suite, the other door will provide safe egress.
Open OBC Div. B 9.9.7.4. in the code viewer