Calculator inputs
Use the responsive form below. It shows three columns on large screens, two on medium screens, and one on mobile.
Example data table
| Scenario | Occupancy | Mount | Room size | Ceiling height | Suggested result |
|---|---|---|---|---|---|
| Open office | Non-sleeping | Wall | 85 ft × 55 ft | 12 ft | 2 appliances at 135 cd planning level |
| Training room | Non-sleeping | Ceiling | 48 ft × 40 ft | 18 ft | 1 centered appliance at 95 cd planning level |
| Main corridor | Corridor | Wall | 210 ft × 14 ft | 10 ft | 3 visible appliances at 15 cd minimum |
| Guest room zone | Sleeping | Wall | 18 ft × 16 ft | 9 ft | 177 cd when lens center is under 24 in below ceiling |
Formula used
1) Equivalent design square
Equivalent square = max(cell length, cell width)
Non-square spaces are checked against the smallest square that fully encloses the design cell.
2) Derated allowable square
Adjusted square = reference square × (1 − safety reduction ÷ 100)
This lets you tighten spacing below the reference table when a conservative planning margin is preferred.
3) Appliance count
Count along length = ceil(room length ÷ adjusted square)
Count along width = ceil(room width ÷ adjusted square)
Total appliances = count along length × count along width
4) Corridor rule
If length ≤ 30 ft, count = 1
If length > 30 ft, count = ceil((length − 30) ÷ 100) + 1
5) Sleeping-area candela
If lens center is at least 24 in below ceiling, minimum = 110 cd
If lens center is less than 24 in below ceiling, minimum = 177 cd
How to use this calculator
- Choose the occupancy case. Use non-sleeping room, corridor, or sleeping area.
- Enter room length, room width, and ceiling height in feet.
- Pick wall or ceiling mount for non-sleeping spaces. Corridors and sleeping areas default to visible wall planning logic.
- Use Auto layout for a quick planning recommendation, or Check selected candela to test one candela choice.
- Apply an optional safety reduction when you want tighter spacing than the reference table allows.
- For sleeping areas, enter the distance from the ceiling to the lens center in inches.
- Press Calculate spacing. The result card appears above the form and includes export buttons for CSV and PDF.
Important design notes
- This tool is intended for engineering planning and screening. Final layout approval belongs to the authority having jurisdiction.
- Wall-mounted multiple-appliance results use a conservative repeated design-cell method. Exact perimeter-wall placement should be checked against project drawings.
- Ceiling-mounted calculations assume centered placement within each design cell and ceiling heights up to 30 ft.
- Corridor logic assumes corridor visible appliance rules, including the 20 ft width condition commonly used for 15 cd spacing.
- Sleeping-area output is conservative when bed and pillow positions are unknown. Bed-by-bed placement should always be confirmed.
FAQs
1) What does this calculator estimate?
It estimates planning-level spacing, grid counts, and candela needs for visible notification appliances in rooms, corridors, and sleeping areas.
2) Is this a final compliance document?
No. It is a design aid. Final appliance selection, synchronization, mounting details, and approval still require project drawings, listed product data, and authority review.
3) Why does the calculator use an equivalent square?
Room-spacing references are commonly organized by square room size. The enclosing square provides a conservative way to test rectangular or irregular design cells.
4) When should I use ceiling mount?
Use ceiling mount when the project standard permits it and the device can be centered within the design cell. Off-center ceiling devices need additional verification.
5) Why is there a safety reduction field?
It reduces allowable spacing below the reference maximum. Designers often use this to add conservatism for geometry, furniture, sightlines, or future layout changes.
6) How are corridors handled?
The calculator applies a 15 cd minimum with appliances no more than 15 ft from corridor ends and no more than 100 ft apart.
7) How are sleeping rooms handled?
It uses the 24-inch ceiling offset rule to suggest 110 cd or 177 cd and adds a conservative bed-zone estimate when exact bed locations are unavailable.
8) Can I export the result?
Yes. After calculation, use the CSV button for spreadsheet-ready output or the PDF button for a compact summary report.