Fire Alarm Calculator NFPA 72

Detector spacing calculator for fire alarm designers, installers and inspectors. Smoke and heat detector layout per NFPA 72, with the ceiling-height reduction applied the way the standard actually writes it.

WHAT IT CALCULATES
- Detector count and adjusted spacing for a room of any size
- Smoke detectors: 30 ft listed spacing, 900 sq ft per detector
- Heat detectors: 50 ft listed spacing, 2500 sq ft per detector
- Ceiling height reduction for heat detectors: 0.91 at 12 ft down to 0.34 at 30 ft
- Beamed ceiling correction, 10 percent reduction in effective spacing
- Photoelectric, ionization, fixed temperature and rate-of-rise types

CODE REFERENCES BUILT IN
- NFPA 72 Table 17.6.3.5.1 - heat detector spacing reduction by ceiling height
- NFPA 72 section 17.7 - smoke detector spacing is not reduced by ceiling height
- Above 30 ft the app says performance-based design is required instead of guessing a number

HOW IT WORKS
Enter room length and width, ceiling height, detector type and ceiling construction. You get the detector count, the adjusted spacing, coverage per device and the exact spacing factor used.

CORE FEATURES
- Works 100 percent offline, no signal needed on site
- Calculation history you can reopen and reuse
- PDF export for submittals and field records
- Light and dark themes
- English and Spanish
- Material Design 3 interface

TYPICAL USES
- Checking a layout on site before the devices go up
- Verifying a contractor submittal during plan review
- Sizing during a bid walk without pulling the code book out of the truck
- Backing a field decision with a PDF you can attach to the job file
- Studying for NICET certification

WHAT THE PDF REPORT INCLUDES
- Every input you entered
- The calculated results with units
- Date and time of the calculation

OPTIONAL PRO UPGRADE - $2.99 ONE-TIME IN-APP PURCHASE
The following features require a separate one-time in-app purchase. They are not required to use the calculator:
- Unlimited saved calculation history
- PDF export of results
- Dark theme
- Ad-free experience

WHO IT IS FOR
- Fire protection engineers and system designers
- Sprinkler fitters and installers
- Fire inspectors and AHJ plan reviewers
- Contractors preparing bids and submittals
- NICET candidates and fire protection students

ACCURACY NOTE
Results are a design aid, not a stamped design. Verify against the edition of the standard adopted in your jurisdiction and confirm with the authority having jurisdiction.

Part of FireTools, the fire protection calculator collection. More tools at tradetools.dev/fire