Occupancy and exits calculator
Choose the use and enter the floor area. The calculator reads the occupant number from Table D2D18, then the aggregate exit width the storey needs under D2D8 and whether the Class 9 two-exit trigger in D2D3(4) applies, with the D2D5 travel distance limits summarised beside the result. Enter the exits on the drawings to check them.
What it checks
The same engine as the calculator in AEC Assistant, with every table checked against NCC 2025 or the Standard it calls up. The same inputs always give the same result.
Background: NCC D2D18 occupancy guide
You enter
- Building use and class
- Floor area of the storey
- Exits and aggregate width provided, for comparison
- Whether egress is by a stair steeper than 1:12
It reads from
- NCC 2025 Volume One Table D2D18
- NCC 2025 Volume One D2D8 (exit width), D2D3(4) (number of exits) and D2D5 (travel distances, summarised)
A worked example
The calculator's example inputs, checked.
People accommodated
85
people · requires ≥ 1 m aggregate exit width
85 people, so the storey needs at least 1 exit and an aggregate exit width of at least 1 m (D2D8(1)). The other two-exit triggers and the travel distances are below.
- Design occupancyfloor area ÷ area per person, rounded up = 850 m² ÷ 10 m² = 85 peopleNCC 2025 Vol 1 Table D2D18
- Aggregate exit width1 m for up to 100 people = 1 mNCC 2025 Vol 1 D2D8(1)
- Number of exitsat least 1NCC 2025 Vol 1 D2D3(1)
Questions
How many people does the NCC assume in an office?
Table D2D18 gives 10 m² per person for an office. An 850 m² office floor is therefore assessed for 85 people, which drives the exit count and width.
When does a storey need two exits?
The calculator applies D2D3(4): a Class 9 storey or mezzanine accommodating more than 50 people needs two exits. The other D2D3 triggers, such as an effective height over 25 m or a basement, are named beside the result but not assessed, because they depend on more than the floor area.
More NCC calculators
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- Ramp calculatorWork out the gradient, the length of run or the rise, from a rise or from RLs
- Luminance contrast calculatorEnter two light reflectance values
- Light and ventilation calculatorEnter the floor area and the glazed and openable areas
- Sanitary facilities calculatorChoose the building and enter the number of people
- Gutters and downpipes (Housing Provisions 7.4)Enter the roof catchment and locality
Ask about the exits on your own project
The free plan answers from the National Construction Code, state building and planning legislation, ABCB handbooks, regulator practice notes and codes of practice, with the clause cited. No credit card.