Calculator Inputs
Use common planning factors below. Always verify the final factor against the code adopted for your project location.
Example Data Table
| Space | Occupancy Type | Gross Area | Excluded Area | Usable Area | Factor | Rounded Load |
|---|---|---|---|---|---|---|
| Main Office | Business / Office | 3,000 ft² | 150 ft² | 2,850 ft² | 150 ft²/person | 19 |
| Training Room | Assembly Unconcentrated | 1,200 ft² | 0 ft² | 1,200 ft² | 15 ft²/person | 80 |
| Storage Room | Storage | 900 ft² | 100 ft² | 800 ft² | 300 ft²/person | 3 |
Formula Used
Usable Area = Gross Floor Area − Excluded Area
Raw Occupant Load = Usable Area ÷ Occupant Load Factor
Rounded Occupant Load = Ceiling(Raw Occupant Load)
Adjusted Load = Ceiling(Rounded Occupant Load × (1 + Safety Margin ÷ 100))
This tool supports gross and net planning bases through preset occupancy types. Preset factors are helpful for early design and estimating. Final compliance must match the legally adopted code, space function, and authority requirements for the project site.
How to Use This Calculator
- Enter the project name, code reference, and optional safety margin.
- Add one row for each room, floor area, or occupancy zone.
- Select the occupancy type to load a common planning factor.
- Choose square feet or square meters for that row.
- Enter gross area and any excluded area not counted for occupancy.
- Enable custom factor only when your code review requires a different value.
- Press the calculate button to see totals, detailed rows, and the graph.
- Download the result as CSV or PDF for records and reporting.
Frequently Asked Questions
1. What does occupant load mean?
Occupant load is the estimated number of people a space can safely contain based on floor area and an approved load factor. It helps size exits, circulation, and life safety provisions during planning and code review.
2. Why does the calculator round up?
Occupant load is commonly rounded up because partial people cannot be used in safety planning. Rounding up gives a conservative result for egress sizing, signage, and room capacity evaluation.
3. What is the difference between gross and net area?
Gross area usually counts the larger floor area within surrounding walls. Net area often focuses on occupied usable floor space. The correct basis depends on the adopted code table and the specific room function.
4. Should I exclude furniture, shafts, or fixed equipment areas?
Only exclude areas when the adopted code or your project method allows it. Fixed service spaces, shafts, or inaccessible areas may be removed in planning. Always document the reason for each excluded area.
5. Can I use square meters instead of square feet?
Yes. Each row allows square feet or square meters. The preset factor changes with the selected unit, so the calculated load stays consistent with that unit choice.
6. When should I use a custom factor?
Use a custom factor when the project code table, authority guidance, or a validated design assumption differs from the default planning preset. Keep a record of the source behind any custom value.
7. Does this tool replace code review?
No. This calculator supports planning, checking, and documentation. Final approval still depends on the adopted code, occupancy classification, mixed use conditions, and the local authority having jurisdiction.
8. Why add a safety margin?
A safety margin can help with early design allowances, event planning, or conservative checks. It does not override code tables, but it can highlight whether a layout is getting close to a practical limit.